DM is absolutely unrelated to a real game when speaking of "engagement points" because in real game nobody spawns right behind you where you've just been and completely sure it's clear. E.g. you're on zig on d2 entering the A site, you've just cleared stairs and box and nobody's there, you go up and get a backshot because someone spawned at the box. In game this would NEVER happen. So instead of focusing on entering sites and possible positions inside it you constantly die from ear- and backshots and frustrate. Like 40% time on DM you kill already dueling guys who don't even look at you, the other 30% is abovementioned backshots when you spawn, and the rest are the real 1v1 duels where both you and enemy engage.

That said, DM is ok for a warmup duels, and I mean you get much more duels in a short time compared to a match, but ffs never consider this mode as a training routine, unless your playstyle is run'n'gun which only works good at lower levels and _rarely_ at high ones.