as someone who actually enjoys captaining, my biggest annoyance with the faceit system is having no idea what classes the people I pick are gonna be on before the game starts- obviously this is most noticeable with medic, but it's true throughout
for instance, here are some scenarios that come up a lot
1) there's a pretty good medic main added. I am dubious that he is actually going to be willing to play medic, and he's mediocre on other classes, but I feel like I have to pick him because a) if I don't I'll have literally 0 medic and b) if the other guy picks him and he IS willing to play medic we basically autolose. I pick him like 3rd or something, he refuses to med, my 1st pick and/or the random amateur player who got moved up is forced to medic, and we lose.
2) I recognize that the other team is gonna be on some main class tryhard shit, and I pick the best remaining scouts because that's the most important class for winning pugs in most instances. one or both of them decide to play diff classes and it turns out picking the low IM soldier with decent dm who got lastpicked would have actually been better, despite that being almost impossible to predict ahead of time.
3) I have a very strong idea of what class I want to play, either because it's the one I'm in the mood for or because it's my best class and I want to win. for me, that class is usually demoman. so, I deliberately don't pick any of the one-trick demo mains that advanced is filled with, ensuring that I can play it, or so I think. I join the server very fast, but there's one dude in it already- my teammate, the scout/soldier main, already on demo.
for control freaks who actually enjoy captaining, or at least enjoyed it on pugchamp, it's super frustrating when you're this subject to random luck (I haven't even gotten into the advantages of 1st pick when there's a really obvious fatkid, or being forced to play with people you just don't get along with on a personal level). you wanna believe that, other than your skill vs the skill of the other captain which is obviously a factor, and who gets first pick because someone has to, you actually have a ton of control over your own fate based on how well you captain. in faceit, you just don't.