Well, maybe we need to be the change we'd like to see in the community? Idk, I'm pretty lazy and busy so if I tried I'd probably give up after a few weeks
Toekneegee
I always over plan things. I'll plan encounters appropriate to level. I'll plan NPCs. I'll plan dungeon themes. But I won't plan a dungeon themed encounter unless I know they're heading into that dungeon because it's where we ended the last session.
To put it another way: I never plan so specifically that a thing can't be moved to another place unless I'm positive it's coming next.
I almost bet the GM found a map they thought looked cool and is just throwing stuff at you to fight because it's faster and easier than coming up with storylines and characters with motivations. I get it, we GMs get busy with life and stuff too, but if you've been doing this for a while, there's always a reserve of characters or stories that you made but didn't use which can be pulled into the current game. With a new GM, they may not have that luxury.
All that said, the best course of action seems to be the thing you've already concluded: talk to the GM and the group. Maybe let someone else try being GM if it's just the case of the current one being busy. As others have said, running a prewritten campaign is just fine, especially in Pathfinder. Heck, you can even buy many of them as foundry modules with music, maps and handouts all ready.
I made some Orange chicken, steamed broccoli and white rice.
All of it is low sodium (I have to eat low sodium for medical reasons) and the chicken was baked instead of fried to keep things from getting too unhealthy