Hehe, much to say here.
I'm not really into variety, I mainly play CTF, so here are a few feedbacks :
- some noobs (not saying it in a pejorative way) maps, I avoid oa_bases maps as I don't feel they are interesting, even the last one (bases7) which is a bit more complex, I almost prefer previous ones. They can be okay to play, but not singular enough. One of them is too bright (all white) with vertex and my brightness. And as Rudy says, there has to be a variety of level for a variety of skill.
- some noob servers, such as instagib ; popular because it doesn't require much skill except moving the mouse and zooming. People like the fact it's easy to kill, and it is impossible for them against some good players who often have good armor and bash noobs too easily, it gives them the feeling they achieved something at least.
- I'm suprised ps37ctf is quite okay to play, it's simple in its layout, still we can have good use of weapons (maybe railgun, nailgun, RL... are well placed). So if I regret its simplicity, it is mostly because of its appearence (no nice buildings to look at

).
- ctf_gate1 is well made (I like its style), but gameplay is average, maybe there isn't enough space to fight, maybe it's more about avoiding people and hiding on some column (I'm not sure of the word) than using weapons to Woot

- ctf_compromise, fog prevents me from playing, I don't like to play with such reduced visibility. Try to remove it, then people may try it.
- ctf4ish is annoying mainly if there are dedicated campers who do their job well. This is different from good railers, even if I find its use not challenging. Otherwise It's great and I have much fun with rockets and air frags (the only map with which I can both play and enjoy spectacular shoots :p). I have fun both with standard ctf4ish and ctf4ishum1.
- I didn't like oasago at first, I felt it was too much about exhausting ourselves running and being fragged when arrived near the flag (so, a bit like what Hydronex can be even if smaller). But it seems in the last games I played there wasn't that much defense, or it was interesting to fight it. Maybe removing the mines helped. I appreciate the gameplay, but maybe lightning gun is too powerful. I suppose I'd consider fun its use if I practiced it more.
- cbctf1 : lol, servers using it are desert, so they are used by people who learn to play online. It hurts too much to make the way to the flag while jumping, too great distance to achieve, not intense enough gameplay.
- ctf2 : it's an okay map, even if a bit limited to catching the railgun, as people are forced to make high and long jumps, they can't be shoot easily with other weapons. Only one RL at each side also makes people less keen on using it. (the central RL on ctf4ish, and one at each side, is a better layout).
- czestxctf ; they seem well made, and both are okay for gameplay, I don't even know what to say about them

Maybe I should play them more.
- delta, does this map ever exist ?

I rarely see it on servers ; It's confusing at first, mainly about moving all the time, and pray other players gone mad so that they lost their way, frag the few ones you meet... but fights may be quite simple (you only walk on one space platform all along, and you can't move much : kill or be killed

)
- islandctf : erf, too long way to the flag.
- oa_spirit3 : hard to judge, quite a nice map, but still I think I'd prefer if there were more battlefields. Think oasago, anywhere you are you can choose a weapon and have a good fight with it.
- Oh I nearly forgot pul1ctf

, I mostly appreciate the textures (half joking, I like the style), interesting frag possibilities, interesting paths to follow while strafing and eventually rocketjumping (it surprisingly seems easy to do and can become quite a short way to the flag, distances between jumps are well measured). Tiers are well used. If you see an enemy coming on a different tier, you can easily take some path to make sure you'll meet him, and not only look at him with your poor weapon and angle which make it hard to hit (thinking of ctf_gate1).
Oh crap, It may be easy to say I don't enjoy, but hard to formalize critics, and harder to positively describe what a map should be.
I know most admins of the server you're refering to. About tarpit, do not confuse automatic kicks (which were sometimes annoying indeed) and ones made by admins.
If this is a human kick, it could both be a matter of cacacacamping (as this is hard to define, maybe they tend to judge a bit too quick) but also of attitude (if you're a bit rude, language as a barrier too, it's sad but maybe you're more friendly with users who use your mother tongue, and less friendly if you hardly understand the foreign language). If you really try to discuss I doubt they'd be that close-minded though. But I'd say I agree as I disapprove the trend to kick in the overall.
As for OA's low popularity ... simple answer : overall quality ?
People who are interested in Q3's gameplay have enough of Q3 ? (Does World of padman use Q3 engine ? I have no idea of their popularity. What about Alien Arena ? IIRC both of these games had specific and maybe better graphics, but maybe they spoiled gameplay).
OA also has some specific audience due to the fact it is opensource. I think I'd have paid very few attention to OA if it wasn't, because I almost didn't give a try to other freewares.
Maybe people are also unaware of the fact Q3's gameplay rox! You just have to check what kind of FPS most people play nowadays, it's not hardcore gaming, and they are less inovative in gameplay terms.
Or maybe there's nothing we can do about it, except maybe a bit more of promotion. OA has to make its way to gaming communities, computer users communities, it's nearly about marketing here, or rather : informing people about what OA is.