Skill-gated is any type of game that becomes too hard to play, because of the "skill level" needed to maintain a level of positivity and fun. When players get too good, it forces you to either try and match their skill level or give up playing the game.
Call of Duty has become mainly skill-gated, because of the amount of good players.
I dont think I want to play Fortnite, its too skill-gated.
(insert game name) has become skill-gated.
This is skill-gated.