Are you saying its too frequent? My concern was PF2 I had the lowest amount of critical rolls ever. Getting criticals is fun, but I do see a problem with them becoming too frequent at <5>.
I don't see how this is possible. In DD3.5 and PF1, you only get a critical hit on a nat 20, and must still confirm that critical with an additional roll (with the exception of a few weapons with expanded crit ranges).
In PF2, nearly every nat 20 is a critical hit (unless that roll would actually be a miss, which is fairly infrequent outside of 3rd attacks) and you also get a critical hit whenever your total score is 10 points or more over the adversary's AC.
What I'm hearing from other folks is a very valid criticism: in most published PF2 adventures and APs (from Paizo, of course) there is a marked propensity for using adversaries that are 3 or 4 levels above the PCs' level. This leads to the feeling that adversaries get very frequent critical hits, and very rarely suffer from critical hits themselves. This feeling is of course completely justified, and it's the way the system was built to work.
Now, I do realize that this is expressly allowed for in the Building Encounters guidelines. Level +3 and +4 adversaries are slotted right into this system.
But my experience (and a whole slew of comments on Discord and forums) shows that is a mistake. Perhaps a highly experienced team of players can field such adversaries without breaking a sweat. On a lucky day. But my group is having a lot more fun facing larger numbers of lesser adversaries. My group has reached 12th level, and very rarely do I go above a level +2 adversary. Just last night, they faced a 14th-level foe who they could barely touch - although his judicious use of a pre-cast Air Walk spell had a lot to do with that, too.
My advice to folks running homebrewed or adapted PF2 adventures is to avoid adversaries more than one level above the PCs for the first few levels (say, 1-4), stretch up to two levels above them for a bit (say, levels 5 to 8 or 10) and hold off on the really out-of-their league foes until they've graduated into the mid to upper levels of character advancement. Or if it turns out that they are having a cakewalk with what you've been serving up, and then pump up the volume.
Aside from this single caveat about higher-level adversaries (PC level +3 or +4) I think the Building Encounters guidelines work very well.