One key criticism of this game is the significantly higher difficulty even on Normal, but it makes sense when you think about it. The loss of Shanoa's memories has pretty much left her with none of her fighting skill, and as Barlowe mentions, he basically has to retrain her from step one and do so in a hurry since there's no time to waste in going after Albus. That lie aside, Shanoa essentially starts out as an inexperienced newbie with no skill, no experience, and next to no training, so she's going to have to learn on the fly in order to survive, a significantly more daunting task than, say, someone like Alucard or a Belmont taking up the quest.
Another potential reason for this is because despite being sealed, Dracula's power is able to corrupt people who are simply studying the seal, which means it's likely his power has been bleeding into the surrounding landscape. Albus has also been wandering the realm trying to study Dominus, which also could leak Dracula's power. So while Barlowe does want Shanoa alive and trains her for this, he also can't help the fact that Dracula's power is making enemies stronger than they should be.
Shanoa's design, while obviously fairly Fanservice-y is also due to practicality as a result of her powers, requiring her back and arms to be exposed. As a result, her boots, chest, and wrists are the only parts of her body that are armored while the rest is a flowing dress. Even with better armor, she would still theoretically need to keep these portions of her body exposed in order to utilize and absorb glyphs, meaning even at her best, she's still nowhere near as tanky as your typical Castlevania hero.
All of the Villagers talents turn out to be something the Belmont lineage needs to make use of or has learned throughout the ages to aid in vampire hunting.
Father Nikolai is an ordained priest. He could easily get access to or create crosses or holy water needed to repel the unholy forces of Dracula.
Jacob is a shopkeeper. The Belmonts have likely made use of the many items or money they've procured from Dracula's Castle, returning anything Dracula had taken into their local establishments. They also may have needed to make plenty of purchases from other people as well to keep stocks of medicine, armor, weapons and ingredients for food or alchemy and whatnot.
Abram was once a thief but turned to making medicines. Consider how the Laurel Subweapon in some of the previous titles allowed for healing, and the fact his medicines make use of herbal curatives and some monster parts (Mandragora Root and Merman Meat anyone?), which Belmonts could reasonably attain due to their profession.
Eugen is a blacksmith. Many of the previous games included whip upgrades or subweapon upgrades, so it makes sense if the Belmonts learned to better craft their weapons to be at their best forms possible as a trade.
Monika is a seamstress. Similarly to Eugen, the Belmonts likely needed to learn weaving to make better clothes or to patch up clothes torn in the course of their monster hunting.
Laura is a jeweler. Similarly to Eugen and Monika, the Belmonts likely found uses for jewels if they aided against monsters in some fashion. Leon for example had an accessory that allowed him to utilize jewels in different ways, and Laura outright knows how certain jewels can aid the effectiveness of elements as well as serving as protective charms against evil Spirits, like in Anna's quest.
George is an musician. It's highly likely given Dracula's classy tastes and the stories the clan would've accumulated from their hunts, someone sooner or later would've started composing songs or stories around their exploits.
Aeon is a chef. The Belmonts would likely need nutritious meals to remain in top physical form, plus they've always found all sorts of food in Dracula's castle that let them heal to full strength.
Marcel is a news reporter who has an interest in the monsters that roam the landscape. It's likely that throughout the ages, the Belmonts would've eventually made use of a Bestiary to keep track of monsters of all stripes in order to know what they face against and how to best kill it.
Anna is a child who seems to have some form of extra-sensory abilities and a somewhat magical bond with her cat, Tom. As Juste has shown, Belmonts have eventually taken to magical learning and can make use of it due to the eventual mixing of the Belnades clan into theirs. Not to mention Maria Renard is related as well, so it makes sense that someone down the line would manifest her powers.
Serge on the other hand is mostly interested in games with time limits, but some of them can be seen as vital tactics the Belmonts have to develop. Hide and Seek becomes vital when one has to quickly and efficiently seek out survivors and/or monsters in their midst, and finding Serge while blinded is reminiscent of how most of the Belmont's quarry hide or fight in the dark, in which case hearing out where the monsters are at is necessary if they want to survive and/or kill them.
Daniela almost seems like an exception, given she's old and wants to enjoy her last memories. However, the fact she asks for sketches of places can be taken akin to cartography, which is a good talent to keep when one wants to think of monsters dens and how they'd look.
Finally, Irina is the mother of Anna and Serge and seems to want Shanoa to slay certain amounts of monsters that she seems to catch wind or rumors of. The Belmonts likely keep their ears open for growing rumors and hearsay as it could lead them to the monsters in the midst of humans, not to mention they could likely kill off certain populations or quotas of monsters in order to know whether they've culled enough to no longer be a problem for people in the area.
Canonically, nothing Shanoa throws at Dracula does anything to him until she finally uses Dominus as her last resort, which works. This fact doesn't exactly highlight that the Belmonts are inherently better at Dracula-slaying than regular folks or that Vampire Killer is the only weapon known to be able to actually hurt Dracula, but instead, this serves as a reminder that Dracula is so powerful that only his own power can stand up against him. Remember Lament of Innocence: The Vampire Killer is made with the soul of Sara, who at that time has been vampirized and about to turn, thus essentially it becomes a weapon that is imbued with some vampiric essence which makes it exceptionally effective against vampires such as Walter and Dracula. The same situation applies to Dominus Glyphs: It is made from Dracula's powers, hence it is capable of harming Dracula.
Similarly, without the Dominus Shanoa cannot win the fight, as once she's done enough damage he does a One-Hit Kill blast if you don't take him out with the Dominus first. The second phase of the fight is also him dropping his usual methods of combat in favor of Good Old Fisticuffs, destructive kicks, and various spells trying to overwhelm her with sheer force. Dracula never transforms, meaning while he decided to let loose, he was never really overwhelmed or even considering himself in danger of being defeated the whole time; were it not for Barlowe harnessing Dracula's power to create the Dominus, Shanoa is so completely and utterly out of her depth and lacking Belmont advantages that Dracula would be a Hopeless Boss Fight without exception.
During their second meeting in the Giant's Dwelling, where Albus gives Shanoa the second piece of Dominus, he asks her to cry for him as, when they were children, he used to feel sorry for her and let her catch him in their games in the past when she would. It comes across as a Kick the Dog moment as it's been shown multiple times she CANNOT feel emotion or remember any of this as a result of his interference, but in light of the coming twist, it actually makes sense. He's testing her to see if she's been able to regain any of her memories or emotions as a result of regaining the first Dominus piece, and by extension if she's still a pawn of Barlowe carrying out his orders with no idea that anything could possibly be off. It's only when she reiterates that he should know damn well she can't remember or feel any of this that he brushes it off and gives her the second Dominus piece. She basically confirmed she's still a clueless pawn and more than ever, he MUST understand how to wield Dominus himself before it's too late and she falls victim to Barlowe's deception.
Dominus is Dracula's power; using it is essentially equivalent to invocating the powers of Chaos itself, explaining why it comes at such a steep price: only the Dark Lord himself can properly wield an unholy power that he gained in a Deal with the Reaper. A "regular" human is doomed to have their soul taken as tribute, possibly an effect of Soul Steal/the Power of Dominance.
Additionally, Albus' soul was taken by Dominus; does that mean his soul is confined within Chaos or Dracula? At least, until either Julius or Soma inadvertently frees it 200 years later by destroying Dracula/Chaos.
Just how does Barlowe get influenced by Dracula? The Inferno Seal is in plain sight right inside his room and in a way where he will easily come into contact with it.
