In a the expansive world of Marvel comics, seeing its iconic characters come together in a team or to fight big villains is one of its main draws. Just look at the Marvel Cinematic Universe as the best example.
Similarly, Marvel Rivals was built on the concept of Team-Up Abilities, which are unique perks or abilities that characters get when paired up with certain other heroes. But for the first time, in season nine, they truly feel substantial thanks to a huge change.