When it comes to WWE, the person who tends to get criticized when things don't go well is Vince McMahon. Why? Because it's his company and he's the man who makes all the final decisions when it comes to...well...anything concerning his company. Sure, WWE is a publicly traded company so Vince doesn't "technically" own it, but the way the company is structured in terms of stock shares and voting power pretty much gives Vince the same sort of power he'd have if WWE were still a privately owned company. Vince has like 90%+ of the voting power and owns somewhere close to half the stock, which means that Vince's net worth right now is probably just a little bit over the $2 billion mark. Now, when you're someone who wants as much control as Vince does, then, in my eyes, that means you're someone who has to take it on the chin when it comes to criticism because the buck stops with him. Nothing goes down in WWE without Vince McMahon's approval, even if it's an idea he doesn't come up with, he's still the one who endorses it and who's endorsement matters the most.
With that being said, however, Vince is also someone who doesn't get remotely the sort of credit he deserves. People are quick to jump down his throat over the tiniest little thing but praise fro a job well done or decisions made are extremely, extremely slow in coming from a lot of internet fans and may dirt sheet writers. I pecker slap Vince as much as anyone when I think he's making bad decisions, but I do have to give the man credit; I don't think he's as strong on the creative end of things as he once was but he's still got the corporate aspects of things down.
I'm of the opinion that there doens't need to be a singular face for WWE. Vince putting all of his eggs, or at least most of them, in one basket, as we saw with John Cena beginning in the mid 2000s, did sometimes result in boring feuds, a stale & sterilized creative process and an underpowered roster because damn near everyone Cena faced for a long time never came off as a credible threat to him. When you look at the WWE roster right now, there are wrestlers who have the crediblity, while some have the credibility, to step up into the top spot of the company without seeming like placeholders ready to hand it back to Cena, or Roman Reigns in this case because Reigns hasn't been built up to the ridiculous level Cena was during the peak of his career.
The roster is important in the sense that the roster is what sells the product, you can't have a wrestling company without wrestlers that people want to see wrestle. However, if Roman Reigns left tomorrow, it wouldn't impact WWE's bottom line one iota. If WWE could survive Daniel Bryan having to leave, a wrestler who was the most popular on the roster, sold a lot of merchandise, helped sell a lot of tickets and who's segments/matches were often the most watched parts of WWE TV, then the machine will chug along just fine if/when anyone else on the roster leaves. One of the few to create even a ripple would be Brock Lesnar but it's not like Lesnar is bringing in record ratings or anything.