I played a wizard in our game (up to level 5). It seemed to be consistently underpowered compared to the other characters.
From reading a lot of discussion on the Paizo forums, there seem to be two things that lead to this impression (and note, that is not me saying that its entirely incorrect, just that whether it is or not it seems so for these reasons):
1. In general, spellcasters have been cut back some from 3e era ones. That's because (and I know this doesn't go over well with some, but I don't know any better way to put it that is honest) they were out of balance with non-casters. That was just taken as a given by a lot of people and was viewed as somehow okay by many, but that didn't make it good design and one of the design choices in PF2e was to push the two types together. One of the areas where this is very visible is that spellcasting is generally a weak way to directly deal with a single opponent--and that's probably the single most visible sign of effectiveness that most people percieve. Spellcasting can still be a good way to start cooking up groups when a spell caster is willing to take some positioning chance, and good ways to buff and debuff (but as I noted, people who haven't internalized the importance of manipulating crit and fumble chances don't always see it that way), but neither of these tends to be as visible (and of course occasionally you'll get GMs who make it really hard to apply the first; personally, I've watched one players lightning-oriented sorcerers dump more damage out on a semi consistent basis than either of my fighting types did, she just doesn't do it all in one place).
2. Getting full value out of prepared spellcasters can sometimes be tricky, and if a group is not good at information gathering it can be trickier yet. This isn't as big a problem with clerics as it is with wizards, so it isn't quite as visible there. In addition, they were probably more conservative with wizard focus spells than they really needed to be, so a lot of people find them underwhelming.
That said, wizards are still perfectly functional, especially universalist wizards (who aren't dependent on getting value out of questionable focus spells); you have to simply do a general utility spell set you default to and only change up when you have better information. You can argue at that point you might as well played a sorcerer (and on those occasions when you don't have information, you're not wrong exactly), but when you
do have information you have a lot more capability to bake a cake. But it requires the willingness to do that, and a GM who doesn't resist it heavily. If neither of those is the case, a wizard will probably suffer compared to a sorcerer.