Actually Slimes don't work anymore i tried it with my own /pet slime:large and /pet rider slime:large.
Actually, I think all pets should be removed, we can still stack pets(cows, sheep etc) and they would still block most attacks.
Dont remove pets just remove slimes and magma cubes from infection or maybe can we just have pets like skeletons, creepers, endermen, bats, and all the other small pets