I'm a fan of Crash Site and Complex, but I'm a weirdo. I like bad clusterfuck things lol. I really like the uphill/downhill battle on Crash Site, it feels like a campaign scenario with real people fighting. Also the visuals design of the environment areas are a reason I like it, it looks amazing and like a real place a battle is taking place in and not just an arena made for this game. Which is why some people don't like it, that it doesn't have very obvious wall running paths and stuff but I like the rugged environment. I don't really think it should be expected to be able to ski at crazy high speeds on every single map. A lot of different pretty areas in the map. Complex as well is really visually interesting with all it's different looking areas that surround the main hallway. I understand with Titans being cramped in that hallway but you don't have to always go in there, I personally think it's hilarious in there. I think that one is actually a pretty good map whereas I understand most of the complaints of Crash Site.
Also I play Attrition 95% of the time so how bad they might be in other modes doesn't factor into my opinion of them...