It's a POV thing in some cases. For example, fewer options for character creation is seen as giving a boring and limited ruleset by 3.5 players, and wonderfully freeing by old-school players. No feat chains, no trap options, no needing the drawing my sword feat just to draw swords. Now what you can do is limited only by your situational awareness, imagination, and dialogue with the DM (which if you're from the Frank Trollman school is akin to being held hostage by the DM, but you can't solve stupid).
The combination of the Reaction Chart, Morale rules, and gold for XP creates an entirely separate playstyle than later games, one focused on negotiation, trickery, and stealth rather than "slay everything you encounter because it's there to be farmed for XP." Encounters play out radically different. If you try playing old-school encounters as you would in new games, you will die and think the game is immensely unfair, when it's only that you were unable to question your assumptions of what monsters "were there for".
Greater acceptance of death and risk thereof leads to a very different playstyle, as you can imagine. You probably don't have a hero/plot shield (you might a bit, because you can run a more heroic OSR game, but I wouldn't say that's the prevailing tendency).
Modules or not, old-school gaming is much more freeform. Players often do what they want, rather than being force-fed the adventure. If you've ever played a sandbox style game, you know this creates a completely different experience at the table compared to a plot-heavy game. Curiously, people who argue for a Trollman-style view of the players being at the mercy of Evil DM always seem to ignore this part.
LFQW could still be a thing, depending on how you argue what that means, but it's not even remotely as bad as later editions for several key reasons.
I also wouldn't say it's mathematically worse than PF, if only because there's a lot fewer math points to abuse.