What I saw, when I played Pathfinder public play, was that if you didn't make the best choices when creating your character, you tended to have a bad experience. It wasn't like the adventures required optimization, but if you sit down at a table with four other players, and they all have cracked out characters and you didn't, it was pretty miserable when your contributions either didn't matter, or worse, you were just holding the group back.
I always found it strange, you build a game with choices, some better than others. Then if a player makes good choices, the game's challenge literally falls apart. A good example of this was my roommate.
He wanted to play an archer in Pathfinder. So he decided "well, Fighter is best at fighting, so I'll be a Fighter". He didn't even take an archetype, he just gave himself good Str/Dex, and took all the archery Feats he qualified for.
And he was a holy terror, full attacking the instant his initiative came up (often before the enemies because of his 22 Dex), making four attacks per turn thanks to Rapid Shot and some other Feat that let him fire another arrow (the name of which is eluding me right now...Manyshot?). He could fire arrows into melee, and even damage reduction was little more than a speed bump because he could add all his damage together before DR was applied thanks to Clustered Shots.
This was at like, level 7. We often had fights where he'd have major enemies almost dead before the melee could reach them. And the only thing that could stop him was basically by shutting down his build entirely with miss chances or Wind Wall (and even there, we discovered the system had workarounds for, by picking up specialized arrows).
And this wasn't some outlandish build like "dex magus with scimitar and shocking grasp", this was just "I make a character who is good at bow".
Heck, we had a goblin cavalier in one session. He had a riding dog. He's charging for like 70+ damage because he took a class that's meant for mounted combat, and mounted combat feats. It's no wonder optimization gets a bad name when the game folds in half to a player who says "hey, I'm going to be a cavalier who does cavalier things"!