What I hear, is folks bemoaning the fact that PF2 has fairly tight mechanics dictating what a group of adventurers can and cannot be expected to fight.
While that's true, you also have to account for the DM's instinct, his rule of thumb. You're not going to sic a family of cloud giants or an ancient red dragon on a hapless party of 1st or 2nd-level PCs. An experienced DM is going to adjust the threat to the capabilities of the PCs, on an intuitive level, even if he doesn't take the time to calculate the exact encounter balance using the Building Encounters guidelines.
Sure, you may have some situations where the PCs should objectively take flight and try to evade the overwhelming power of the beasties they have encountered. The players should know their DM well enough that they realize that they can't expect to bull through everything in their path, and sometimes escapaing with their lives is as good a result as they can hope for.
I don't think PF2 is more poorly adapted to this type of creature populating approach than any other RPG. If you want to populate a region with a variety of threats, some of which are beyond the capacity of the PCs to fight toe-to-toe, you can do that, it simply requires the DM to telegraph the severity of the threat, so that it becomes a test of their ability to escape rather than a full frontal combat that they can hope to overcome.
Regardless of the game system you choose to play under, these sorts of situations will require a different approach on the part of the players.