There's nothing stopping kids from playing Faceit rn, almost half the games I get put into have someone that can't be more than 12. But the bright side is at least when you get put on a team with kids they're at least on a similar skill level. Like Global in CS has such a high skill disparity between the bottom and top globals so games are usually always 16-0s or something, thats the main reason I play Faceit because the games are closer and faceit level 6-7 is probably the average skill of a global elite so there's many more ranks to seperate skill.
Imo if Valve simply improves there elo system and maybe gives you an option to see where you place on a leaderboard that would be good enough to convert many faceit players, pros would obviously still use pro league but yk