I agree with that statement, there's no reason to play her the way Marth has normally been played because his playstyle was based almost entirely on his tipper mechanic (and disjoint and reach, but those go along with the tipper). I think its worth noting however, that Lucina has potential to add something new and interesting to smash, that is all!
Wasn't its knockback based on what it countered in brawl? Regardless, certainly sounds like a significant buff to that move. Could give Marth mains a tasty reward for good reads, and Lucina may inherit it. If Marth's counter is that strong... Imagine Ike's.
I am also not convinced Marth is bad enough to warrant dedicated Marth mains switching away from him. He may be nerfed, but his kit is a recipe for success in smash, historically. I expect him to sneak into mid-high tier, despite the nerfs.