Post you want to join a guild, then you join them, and show up to raid.
The only way people can’t, is because they don’t want to try.
Or they want to run their own groups and refuse to join someone else’s.
(That might get me further in m+ department.)
There’s no like large list of teams waiting for me in m+. There are plenty of guilds needing everything except tank I wager. (Tank should be hardest to find a guild for.)