YMMV / Ys IX: Monstrum Nox

• Continuity Lockout: The Reveal that alchemy is responsible for the Monstrums' nature, with Chatelard stating to Adol that this isn't the first time he's seen it in action, ruins the key element and surprise to the story of Ys V: Lost Kefin, Kingdom of Sand. Furthermore, the climax of Ys IX featuring the souls of Feena, Reah, Dark Fact, Eldeel, Tia and Dana from Adol's memories would likely sail over the heads of new players.
• Game-Breaker: White Cat becomes monstrous in game-play once leveled half-way through and properly equipped with Critical Hit/strength-focused equipment. Low base defense? Can't Flash Guard? Wrong damage types? None of that matters when she can use the skill "Rapid Slide" in-and-out of every combat situation, while dealing Critical Hits with a flurry of basic normal attacks and several of her air-stalling skills like "Heavenly Steps" and "Cat Flip". Rapid Slide can also be thoroughly abused while traversing environments due to its very low SP cost, with the only requirement for it being to acquire a specific skill book that unlocks from a Sidequest. With a little time, White Cat can zip around shredding any Mooks and a vast majority of story-mandatory bosses alike to pieces with minimal effort (barring a few Damage Sponge Bosses and those with really large Area of Effect attacks), putting the rest of the party members to shame.
• It's Easy, So It Sucks!: One of the primary criticisms towards Ys IX is that combat feels too simple, with the Flash manuveurs being mostly optional mechanics unless the difficulty level is cranked up (an opinion shared by Zero Punctuation and IGN). That combat is still the same Button Mashing affair also results in the game having shorter play-time on average.
• Scrappy Mechanic: In order to progress the narrative of the game, players must complete Grimwald Nox battles for every barrier leading to the next major story beat, which requires 100 points towards the NOX Gauge, earned either through completing Sidequests or fighting Lemures via black pillars throughout the city. The problem is that it's mandatory in all chapters of Ys IX; contrast "Beast Raids" in Ys VIII: Lacrimosa of Dana, where outside of the introductory Raid, the story remains unaffected if players don't complete subsequent Raids. Furthermore, to unlock more areas of Balduq for exploration and 100% Completion, players need to complete a second one. Fortunately, this doesn't require another 100 points to the NOX Gauge.
• Viewer Gender Confusion: If he wasn't referred with male pronouns by the other characters, players could easily mistake Zola for a woman due to his English dub's delivery.