Here's the thing: Finn Balor has proven to be a really good worker, not just in WWE but also in NXT and NJPW. In the case of NXT, he had some of the best matches the territory ever had: Some of which include (but aren't limited to) those against Neville, Samoa Joe and Kevin Owens. Those who would later reach the main roster themselves. Even today, he's still capable of putting on quality matches. (A.J Styles, Cesaro, Seth Rollins, Roman Reigns, etc.)
And when it comes to his demon alter-ego: It's always a treat to see him in that mindset, and up to this point: He's got the best entrance out of everyone currently in WWE. When he locks himself into 'The Demon', you know things have only gotten too personal for Balor to take lying down.
The problem with Finn Balor is that while he oozes charisma, very little of it actually goes into his mic work.
Don't get me wrong, it's perfectly fine being soft-spoken and articulate during your promos, lots of people have done it before and some of these issues have been because the material wasn't up to snuff: But it doesn't change the fact that sometimes Finn is just very boring to listen to. Every promo we've heard from him since arriving into WWE has been mostly similar to one another, talk about recent events between him and his rival in a generic monotone voice, maybe occasionally show some anger every now and then proceed onward. It's effective yes, but it also makes it slightly repetitive when you have the same rival for weeks without rest. Once in a while, if you want to switch things up you can bring up 'The Demon'.
That's another problem I have with Finn: What is it about The Demon that separates Finn from The Demon? Outside of maybe entrance, they both have the same moveset, most of the same mannerisms, even the same finishers. Nothing new has been added, no stakes have been raised. I hate to say it, but it sort of makes the idea of an alter-ego sort of pointless.
Even so: I don't think that's necessarily the problem with Finn seeing as he still sells well in WWE's store and fans continue to pop for him every time he appears on TV. But I think what's happened with Finn is that he's lost the support of the higher-ups: Why is that? Simple, injuries.
Do you remember back in SummerSlam 2016 he won the Universal Title? That was awesome news. Then one day later, he had to vacate the title because of an arm injury: He wouldn't return until the RAW after WrestleMania 33. Even so, it wouldn't be long until he got injured again on the hands of Jinder Mahal.
When you get injured quickly, management is going to be less willing to push you and once you get labeled with the term 'Injury-prone', that pretty ends any chance you have of being a main-eventer. Thankfully, Finn hasn't gotten injured since: But the fact that Finn got injured not one, but TWICE during big moments for his career is not a very convincing sign that good times are ahead.
So now that we've talked about what's wrong with Finn Balor, what can we do to fix it? Well, I would like to introduce the concept of 'less is more'.
When Finn Balor is himself: You can keep him exactly the same outside of one detail, you make him talk less. Maybe have him do shorter promos, maybe only say a few words, whatever you do: Finn should not speak as much or as long as he does right now. If done right, this helps to give Finn a more bad-ass appeal as a strong, soft-spoken, take no prisoners face who leads by example.
Now what happens when you turn him into The Demon?: Well this is where more comes in, as we all know: There are many moves Finn uses that he has yet to attempt in WWE and if he has, it's a rare moment. Why not WWE let 'The Demon' be where Finn unleashes his most dangerous weapons, such as '1916' (or as it was known in NJPW as Bloody Sunday) or Devitt's End (you could rename it Demon's End if you really wanted to) or maybe even Prince's Throne. I can assume many a fan would love to want to see a WWE match with any of those moves.
In short: Finn is sweet, but he isn't as sweet as some of us make him out to be. But with a few tweaks and a bit of good luck: He could easily make it back in the main event scene.