There are numerous reasons why Roman Reigns being arguably the biggest heel in wrestling is extremely problematic for Vince McMahon. Far more than than the fact he's supposed to be the biggest babyface.
The boos aren't just killing the television product, the main events aren't just killing the pay-per-views, and the promos aren't just killing the matches. A fundamental inability to connect 'The Big Dog' with the audience is murdering the very nature of how characters are constructed. Roman can't choke somebody because the product is PG, but he can't deck somebody from behind because he's supposed to be a 'Good Guy' despite his protestations to the fact shortly after demolishing The Undertaker at WrestleMania 33.
Samoa Joe had no problem taking shortcuts against him, but still couldn't generate hate in response. Nor could he, for that matter, convince Backlash audience members that it was worth sticking around to watch him try. Roman is immune to foul play, salvageable only if he engages in it himself, which doesn't look anymore likely than it has done over the last four years.
The death of the wrestling villain via Reigns is removing the need to be quite as vile, but it really shouldn't. Those that did it well deserved the victories that followed. Roman can't even buy a win these days, he could at least steal one...