So because a new character isn't white and male, it's a gimmick to get an already massive fanbase even larger? Comic books change characters literally all the time throughout the generations. God forbid the Falcon, a verified Captain America fanboy, take up the shield after Steve Rogers.
It's like you don't even know what the word diversity means, lol.
Swapping out the entire main cast of an already established classic after two sequels is a gimmick.
Basically making too many sequels or spinoffs of anything is gimmicky.
The hunger games had a female protagonist and plenty of female characters, but it wasn't a gimmick, because it was its own franchise/IP.
But Ghostbusters already exists, you can't just remake it and forget about everything that happened the last three movies.