Because Rivals 2 add grabbing, there will be shields (at 0:41, you can see Maypul using it), and so, parry too.
Depicts peoples asked to keep the Rivals of Aether DNA (very fast combats) and not add grab/shield, Dan’s (the main dev/designer) thought it add more depth to the fight (and, I suspect, lower the bar of new players and Smash players because you could simply be destroyed in seconds if you were not prepared in original one). While it’s sad to see a specificity of original game removed, I think he is right and this choice will push its IP further.
Ah, and of course, rollback netcode written from scratch. I mean, rollback netcode written from scratch on a second iteration of a beloved platform fighter.