I think it's good for practicing new things like movement but in my opinion it should be seen just for fun because it's not a good way to start off your game. Ever since i started incorporating it as a way of practice/Warming up I got worse and worse in normal games now, I'm still somewhat decent but it's not like I used to(Now ik I'm not going to be the best player in the world but I'm happy slowly getting better) and I get more mad when I die even when I say it's ok it happens.

(I'll add more if I can think of it but please do tell me what your thoughts are on deathmatch because I think it's a great gamemode even if It makes me mad)