Well with 5e at least they've curbed the issue. Having said that, part of the problem has to do with what it means to be a wizard vs. being a fighter or a rogue.
You see, a fighter swings their sword. Swinging a sword can only be so great. By contrast, with a wizard there's so many directions you can go with their abilities that it's absurd.
"Any campaign world where an orc samurai can leap off a landcruiser to fight a herd of Bulbasaurs will always have my vote of confidence"
Think of the mooks!
To some extent, there is a bit of fudge room in regards to it, because it is possible to build your encounters such that it's less of an issue, but it depends in part on the inherent build of the fighter and the wizard in question. That said, the general sense is still true. In the generalized encounter, the wizard is going to have more options, more powerful options, and more definitive options than the fighter.
The main advantage the fighter has is repeatability - their main schtick? They can do it all day, no questions asked. The wizard has only a few chances. The problem with that is that encounter design now is such that people only do one or two a day, so that the wizard can reload spells and thereby eliminate the issue. When I first started, it paid to have a warrior not for the first encounter of the day, but the tenth. You would never see that kind of adventure design anymore.
Also, really, divine full casters are where it's really at. If warrior improvement could be described as X+L (where X is base, L is the effect of leveling up), and wizards could be described as X^L, clerics and druids can be described as X^L+2L.
Reminder: Offscreen Villainy does not count towards Complete Monster.
^I'm honestly confused about what you are talking about because I haven't seen "one encounter adventuring days" in campaigns outside of hexploration campaigns where each hex might have one encounter at most ._. Like, whenever there is dungeon, party tends to go through the dungeon in one day regardless of how many encounters there are(unless they are about to die)
Maybe that is what it is, we don't really have too many one encounter days if we have encounters at all while traveling. Along with that our dungeons tend to be long and difficult.
I am curious about how much other people have seen the effects of Linear Warriors, Quadratic Wizards.
I understand the trope and the theory behind it, but in practice I've not seen it much in my games. Or if it has been there it has been so minor as to not really impact things. So I am not sure, what it is that differ in the games that I play in or run compared to other such that this trope does not pop up.
So I want to know from other players, do your games seem plagued by this? What have you done to curb it? Are you in the same boat and don't seem to notice it?