I'm not sure why you would even play the Monk in D&D 3rd edition or its forks, given how much do they suck in comparison to pretty much any other class in the game.
Yes, why would you ever want to play anything that isn't tier 1, or maybe a tier 2 if the DM bans all those T1 primary casters? They're called rollplaying games for a reason, and you're not having fun if you're not trivializing the rest of the party, right?
Though FWIW it's also something of a mistake to rate classes based on their ideal circumstances. In the 3.5 campaign Remuthra was running until he disappeared, I played a Monk, because I wanted to do a sort of abandoned orphan raised by ancient kung-fu master who dies before completing her training sort of character, who was lawful in spite of her natural proclivity towards violent conflict resolution and working to better herself and seek true enlightenment. I came up with the character concept, then build the crunch around that, starting out with a two-level dip of Monk and then crossing into PsyWar.
Yes, I optimized. Yes, we were using the traditional make-Monks-less-shit houserules re: Unarmed Strike + Gauntlets proficiency and Gauntlets doing Unarmed Strike damage if that's higher while letting you put weapon enhancements on it, full BAB, and then an allowance to make Tashalatora apply to all of the remaining numerically scaling things on the Monk ability list. However! That came after the character was a person, and happened because I wanted to play something that I could have fun with and be interesting with without dragging down the party.
The result? I made people laugh (I think/hope), and despite being in a party with the likes of a Cleric, Wizard, and Archivist, my Monk managed to contribute to the rollplay; both times we had a serious encounter that I was there for, I ran straight in and OHKO'd the boss mook, then ran around and kept punching people out (or trying to). Not that it saved us from the mass Burning Hands crossfires and flesh/skin/hair being counted as "flammable materials"... fuckin' cultists.
But that's not the point. Even if all I was doing in combat was running in and distracting the enemies, that's "good enough", because unless you've got a party full of powergamers and a killer DM, it's about the roleplay, not the rollplay at the end of the day. We spent more time mucking about with cursed weapons, going to the shady-as-fuck everything-dealer, and dragging each other out of burning buildings than we did killing cultists.
See, I fell into a similar trap before - that optimisation and roleplaying is a one-or-the-other situation.
Monk, is at the end of a day, a class. A bad one. You can build a unarmed fighter that works better than a monk and say "This guy is a monk of X temple," and play him as such. And you can't say that's wrong. If it talks like a monk, walks like a monk, and punches (better) than a monk, you can call it a monk even if it's not a Monk.
You played a Monk that had been significally buffed from it's original interpretation. Because if it's too weak that hinders roleplaying, too. A master of martial arts getting chumped by every fighter it comes across is probably antithesis to what you were intending.
There are silly things, like half-dragon half-minotaur half-ogre kobolds, yes. But aside from the really silly things like that an optimised character can provide opportunities. They have a weird combat style - who taught them it? How did they discover it? That sort of stuff still applies.
See, that's the point I was making. That setup was a perfect example of how to meet your baseline for rollplay when you're interested in RP -- the character contributes to the party in a meaningful way. When you want to do something but aren't sure if it's viable, you talk with your DM. And you optimize the shit out of it. The point being to lift a class that wouldn't ordinarily be very viable into a higher tier so that it is. Duh.
If you really want to argue that "no ur not allowed to play anything suboptimal," I'd say fuck your Fighters and Barbarians, you have to play a Warblade, glaivelock, Cleric, or Druid. What, you want to play a martial character without being a caster or using weeaboo fightan magic? Too bad, martial classes are trash.
This whole "bluh bluh you have to only play the best things every time" is, frankly, disgusting and rather detrimental to the medium. If someone wants to play a sword&board Fighter straight up to level 20, I'm going to smile and have fun rather than bitching at them about how they should have played a spiked chain AoO machine or a charger.
But this is starting to derail, so let's continue in the RPG thread if we're going to.
Suboptimal play is good
when you explicitly agree to it with all other people on the table.
The problem is that a lot of people refuse to accept that classes like fighter and monk are
objectively useless in comparison with the same-level wizard/cleric/druid. Anything they can do the magic classes can do better, and there are a lot of things that magic classes can do that are not even an option to non-magic classes.
There's this whole misconception that you can fix a Fighter by giving him more damage/HP, but it's
wrong. He's still useless in most out-of-combat encounters, which BTW are the core of roleplay experience so the non-magic classes fail at roleplaying, too (what a surprise).
And Fighter is just such a trash name for a class. Every class in the game fights, so Fighter is
conceptually limited to be below every single other class in the game just by his name alone. Monk has more potential, but the way he's implemented in D&D 3rd edition is beyond atrocious. The most obvious example of that is that Monks by default for some reason don't have proficiency with their fists. The "lol you can't use both spring attack and flurry of blows at the same time because that would be OP hurr durr" thing is also a fine example of why Monk is bad.
Really the game would benefit greatly if the classes Fighter and Monk were combined with the Paladin class into a single flexible Martial-with-occasional-magical-help character.