Brink was a good game plagued by many things.
One, It was a fun PVP shooter without any good single player content. Yes, you can play against bots but it was a below average experience. You gotta remember it was one of the first to attempt PVP shooter without a single player portion. It was bashed badly in an era when single player was still highly valued.
Two, the matchmaking was completely messed up. It won't balance team based on skills or numbers. Meaning, it can put 6 2.0KD players against 3 0.5KD players. All the while keep pouring more new players onto the team with 6 players.
Three, very, I mean, very steep learning curve. Hard for average played to master in-game mechanics. Players who mastered it have a massive advantage over players who can't. For example, light class (even with less armor and health) moves faster, can wall run, smaller hitbox and combined with grenades shooting talent. Light class was the goto class for any competitive players who mastered the game.
Four, no lucky twitch shooting. No 0.1 second body shot TTK so if you aren't good at the game, you're just screwed.
It was a good PVP shooter but too hardcore for average players. The devs thought too highly of the shooter gaming community and they couldn't make the game into a competitive Esport like CS. The game flopped and tanked.
The game was a pioneer of its time and the gaming community just weren't quite ready for something like it. Heck, I think even the devs themselves weren't ready for what they made.