How often are such games revitalised successfully?
Hellgate London or APB Reloaded happened (and are even still alive?!), so maybe there are some bits to salvage from this too.
It's possible, but it's usually a matter of relaunching a game with potential that was disappointing because of some issues.
FFXIV, Diablo III and Destiny (when they launched TTK) are examples of paid games that launched in a disappointing way but were able to redeem themselves.
The thing is, people wanted to like those games. They were highly anticipated products.
No one wanted Suicide Squad, everybody hated it the second it was shown as a GaaS. I enjoyed the game because I liked the characters and the story, but there's no way it can succeed as a GaaS. There is nothing that will bring people back. I was done the moment I finished the story and will go back when more missions are available. No incentive in getting new gear and new material when there are plenty of other games with more satisfying progression systems. I'm not interested in trying new characters to do the same missions repeatedly.
The weird thing is, the game, in a way, doesn't know what it wants to be. The GaaS stuff is barely there during the campaign, where the focus is mainly on the story. And you can ignore any weapons and equipment because their effect barely makes any difference. Same for the abilities you can unlock. The stuff seems more meaningful in the endgame, but you probably won't care enough to stick around because... it's not fun, and you won't suddenly care after 20 hours. They went with this GaaS approach, but holding back because they were probably thinking "we're Rocksteady, players want story". Which I appreciated, but the game ended up being this weird product that makes no one happy.
tl;dr It can't be revitalized because there isn't a strong core with unfulfilled potential that an update or a rework can fix. And because Helldivers is out and costs half the price, it doesn't try to be more than it is.