What really matters in terms of whether we consider re 6 a failure is how Capcom viewed it, because their response is ultimately what's going to shape the changes going forward, and they did view it as a failure.
I'm well aware of how annoying re fans can be, but I have a hard time believing that Capcom's going to do a total 180 because of some whiny kids on the IGN comment section. Every game has that. God only knows how many people trash cod games, saying stuff like how they're the same game year in and year out or that they should go back to what they did in the pre-black ops era, but guess what? They get ignored, and cod sales are still ridiculously high. They could've decided to revamp the series for a number of reasons, maybe it was the ****tering of their illusions of grandeur with sales of 6, maybe it was the trolls, maybe they were jumping on the bandwagon of other horror games (I'll throat punch the next person who says 7's an outlast/pt clone, but there are certain undeniably similarities), or maybe they wanted the people to draw comparisons to the retroactively ridiculously well received 4. It could be any number of these reasons or more, but I still don't really see a truly convincing reason for the turn they took.
Except even with COD it got to the point where they are going back to pre-sci fi games because people are complaining way too much there too. Also it's not just IGN.
Kotaku, Youtube, Facebook, Twitter, Twitch, Steam, Forums, Discord, IGN, Etc.
Literally at every turn there is someone talking some mad ****. Of course you can ignore it for a while. But if it reaches the point where no matter where you go you see people talking some mad crap over something you poured in hundreds of hours and work into I can guarantee you that you WILL feel some irritation. And with how the gaming industry is becoming with tons of shady crap in the background the motivation and will to make something your 'fans' want are drowned out by what the devs want to do.
These can go two ways.
Companies can listen to fans and risk having those same fans go "SUPERIOR TRASH TALK!" Because it isn't what THEY specifically want. (While only aimed at that niche of fans and potentially have the game bomb.)
Or the Devs can do what THEY want to do and ignore the fans in hopes it draws in some new ones and please the more reasonable old fans.
A lot of game devs go the latter route because the 'Old fans' are a bunch of **** stains. The shift in RE came from trying to keep the game fresh and relevant as they felt that what they did before wasn't going to cut it. And they were right. Of course they ended up ****ing fans of the older games off, but in turn they got new fans. (I am one of those. I don't particularly like the older games as much as I do the more actiony games. Yet, I still do. But I would not have bothered with the series if it kept with that old crappy formula.)
These decisions led to making spin off games that more people can like. ORC is an example. (Every RE "Fan" hates that title because it ain't RE. But I love it. It took what I loved about RE and put it an entirely different type of genre one that was REALLY fun. Despite how buggy some mechanics and animations were.)
Again, ****ed off the older fans so they keep complaining, but this has been going on for years. I believe they've come to realise after RE6, that their only vocal fans are the little whining maggots that still feast on the corpses of old outdated games. You can't get rid of them, they make you money.
So again. What do you do?
You bend to their will so the crying will stop. Even if it's for a little while.