There's been a lot of discussions around the Wizard since the remaster, none of them all that positive. There's a consensus that the class has changed for the worse, and that the general landscape has evolved in a manner that's left them behind, which does not bode well for what seems to be an otherwise flavorful expansion themed entirely around wizarding academies across Golarion. For those who aren't familiar with the discussions already, here I think are some common points:
What's Wrong with the Wizard?:
Because the Wizard's arcane school slot got changed to work only with a limited curriculum of spells, rather than an entire OGL school of magic, the Wizard received a substantial nerf to their versatility. In some cases, this also came at a minor yet symbolic loss in power, as schools like Battle Magic force the class to prepare spells into lower-rank slots that become obsolete when not heightened enough.
Meanwhile, the remaster has seen most other casters buffed, sometimes substantially. The Oracle is now a four-slot caster, the Mystic and Witchwarper from the Starfinder playtest are both four-slot casters, and even the Sorcerer received a wave of buffs. Less directly, non-arcane spell lists received significant benefits with the addition of spirit damage and a host of new and improved spells, shortening the gap between traditions. This has left the Wizard's four-slot casting feeling much less unique, and has made players increasingly question the restrictions placed both upon the class's fourth slot, and their spell slots overall due to the limitations of their spellbook.
Although the Wizard did receive some positive changes, including some better feats, many issues remained largely unaddressed. Experimental Spellshaping is still not a very popular arcane thesis, Spell Substitution still competes with Refocusing, many school spells still aren't very useful, and the class still has only fairly few feats to choose from, especially for what is meant to be one of the four iconic spellcasters for their respective traditions (they have around half the amount of feats as the Bard, Cleric, or Druid). Unlike other spellcasters, they still can't get a pool of 3 Focus Points without taking an archetype, nor can they access the features of a different subclass, such as the curriculum or school spell of a different arcane school. This has led many players to feel like the Wizard has been neglected.
A lot of players have started to reexamine the Wizard in a more critical light: specifically, the class's overwhelming focus on casting arcane spells does not come across as truly unique in a game with plenty more arcane spellcasters. Similarly, their identity as a student of magic, and an intellectual class in general, doesn't particularly get to shine given how they lack feats that let them Recall Knowledge better, or more broady allow them to do more things that don't just involve casting spells.
Despite what appears to be fairly common ground for criticism, there doesn't seem to be much consensus over which direction to take the Wizard: some people want the class to remain a four-slot caster, others don't. Some people want the class to specialize in a particular school of magic, others don't. Some players even challenge the Wizard's spell preparation, as they dislike the inflexibility of Vancian spellcasting. It seems there are about as many different identities for the Wizard as there are players with an opinion on the Wizard, which makes it difficult to come up with a solution that satisfies everyone.
In short: the Wizard fell behind at a time where every other caster pulled significantly ahead, and as a result people are questioning their place in a game where their power struggles to stand out, and their flaws have become much more apparent. Lots of players want a new and better Wizard, but nobody can agree upon what that Wizard would look like, and so most threads critiquing the class often devolve into squabbling.
With this in mind, I can't really claim to offer a one-size-fits-all solution, because I don't think one exists for this particular problem: I do, however, think there is an approach to take here that could satisfy a greater number of players, and that is to let the player choose what they want the Wizard's specialty to be. If you're interested in specific details, I wrote a 25-page Wizard homebrew that adopts this approach. Beyond those specifics, here I think are the broad lines of how the Wizard could be improved, in whichever form that takes:
Power Concentrated into Arcane Thesis: On one hand, players can't seem to decide what the Wizard is meant to excel at. On the other, many players also want their arcane thesis to be more impactful. I think the Wizard's arcane thesis is the key to giving players what they want here: by no longer making the class a four-slot caster by default, that I think leaves a lot more room in the power budget for much stronger theses. Do you want to cast spellshapes as free actions from level 1? Do you want to shake off the limitations of prepared casting and gain the benefits of flexible spellcasting, without the drawbacks? Do you want to remain a 4-slot caster, but don't want your fourth slot to be restricted to a curriculum? In all of these cases and more, I think there's ample room to deliver that with a playstyle-defining subclass choice.
More Schools: One thing I think many of us are waiting for is a larger number of arcane schools, particularly as the Wizard ended up with fewer schools post-remaster, and the only school they got since is a reskin of the School of Mentalism. I suspect this is something Rival Academies will help with, and I think there's a prime opportunity here to take the Elementalist's elemental schools and make them proper schools for the core Wizard, as well as adapt the Runelord schools to a post-remaster 2e as arcane schools of their own.
More Feats: You can't go wrong with more feats, and with the Wizard there's a lot left to explore, in my opinion. In particular, I think there's plenty of room for feats that improve the Wizard's Lore skills and ability to Recall Knowledge, feats that let a Wizard gain some benefits from a different arcane school, and feats that build on the Wizard's arcane thesis.
In short, give the Wizard lots more options, but also make their arcane thesis the main feature that defines what the class excels at. I think there's room for more specific changes, like making Spell Substitution core to the class instead of their arcane bond feature and allowing the Wizard to substitute spells while Refocusing, but otherwise this sort of framework where each arcane thesis gets a lot more power I think would have a much better chance of tailoring the Wizard to the specific desires of different players than their current structure. You could have your spell battery Wizards, your spellshape-centric Wizards, and even your specialist Wizards all in one, and each would get to shine in their own specific way.
The school/curriculum has a lot of flavor potential, but you don't want every wizard from the same school to be the same.
The thesis makes for another big thing to build flavor around, but again you don't want all wizards with the same thesis to feel the same.
But combining school X thesis, you get a lot of different wizards, while keeping the main character building choices of the class quite clear.
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And yeah, making spell substitution a core feature feels right. Wizard is thematically "the" preparation&adaptation class. Clerics and druids get to prepare from their whole list. It'd be a good contrast if wizards got to change their mind more easily.
