Endzones celebrations are part of the game, and if players want to express their joy for the game, let them. If the other team doesn’t like it, they can just hit harder and play harder, and most importantly not allow so many touchdowns.
I think it oughta come down to the team’s rights. Why should the league determine what is excessive and unsportsmanlike? Let the coaches decide what’s appropriate. If not the coach, at least the organizational leaders.
No celebrations that are dangerous. No lengthy celebrations that slow down the pace of game.
Nothing obscene (No penis cakes wheeled out).
No unreasonable usage of props (No type of celebratory cakes wheeled out at all please).