It's not really about any specific crew, it's about their gameplay which ruins the other (not dmer's kind) of game. I don't think people are complaining about Crews, but the amount of DM in general, which unfortunately is caused by the rules. Of course, certain amount of killing will always be present, and that is alright because otherwise the game wouldn't be appealing, however certain scenarios just make me personally close the game and I know i'm not the only one.
Some people join here just to chill, yet they can't really play in peace. You can't even start trucking because some clown might come to you and kill you in order to "steal your vehicle". You as a cop can't collect tikis or do anything in public, hell, you can't even stay AFK for a few seconds inside the freaking police department because civilians are able to use guns and they made it their playground. The moment you spawn as a cop you are in danger. Anyone with a wanted level is free to kill you regardless of what you're doing.
Because of the "protecting your friend is okay" combined with the stuff i said above, cops on this server are a joke. Seriously though, no one is "scared" when they see you around. You can literally fuck around with them, pretend you have no guns let him cuff you then your 4 friends just destroy him. It makes no sense to play as a cop, for me at least. Go arrest some random on the street, anyone (closeby) can kill you and just say "hey, he's my friend". Also the cop rewards suck, I know this is out of topic, but let me just say a few quick words: most criminals are armed, meaning you lose both guns, armor, health, possibly a car, fuel and all that..and even if you win all you get is like $300 which doesn't cover up a single loss from the list above. Civilians in a single bank rob (which is super easy considering there are a dozen civilians there and cops have no chance) sometimes get like 100x the cash cop's do. Literally..I need to do 100 arrests, while some dude can just pick a free moneybag in already a empty bank and get it in like 1 minute (and for 100 arrests it takes me uhmm..dunno, you calculate it).
So uhmm tldr; rules are making this a sort of DM server, if you're going to change anything it should be that. Crews aren't really a problem, since they don't even fight each other (which is kinda the meaning of gangs, right? lol..wack leaders). Not sure what crew system brings, or how it would affect the current game, but imo crews now are fine. I'm saying they're fine because they don't do any more damage than people who play together but aren't in crews.. However, the fact that different crews team up to kill cops together..that just kills off the whole meaning of this server. What it should be is that they should kill each other in order to get a moneybag, not help each other out. Maybe consider lowering the amount of moneybags (in bank) to like 3.
Over at other CnR servers some balance exists. Of course, different servers, different features, different gameplay. However, the similarity is that both civilians and cops are balanced. This unfortunately isn't the case here. Cops are a joke and that's the reality. If you're okay with 20 civilians killing cops in bank, then consider removing the 'always arrest if the guy is unarmed'. It's entirely up to you what you want this server to be, more RPish or more DMish, but make it balanced. If civilians are free to kill anyone for petty reasons you can't burden cops with 100 rules to always preserve life when possible..it just doesn't work. This is still a relatively new server, it isn't too late to change the rules. Blame the players, honestly.. We wouldn't be here bitching if the players didn't push us to. I know this is kind of a long "tldr", but cba editing it..I just wanted to share my opinion.
So basically, if you want to lower DM, you should change the rules. No more protecting friends UNLESS they are in your car thus in danger. No killing over petty reasons, like wanting ur car(since they can just spam F to take it away) or killing cops based on the color of your nametag.
Or, if you want to keep the above, let cops kill criminals instead of arresting them. Boost their pay, maybe toss in some better weapons or cars with more hp so they actually stand a chance. It probably won't be enough, but it's a start. Oh right, also remove the ability for gang members to change to cops so they can't just bail their friends out.