Of course you're right if you just redefine everything to meet your own criteria. That's not really the case though. Everyone one else in the industry considers all of those games to be Role Playing Games.
I don't know how you could genuinely say that a game where you play as a Paladin/Necromancer/Barbarian etc. With other people online to complete quests, level up and loot gear could ever not be considered role playing. That's pretty much the definition of role play.
Your essentially saying that role playing games haven't existed since the mid 2000s.
And Skyrim? Are there different plot outcomes in that game? I'm pretty sure the main quest is the same for everyone no matter what you do.
Yes back in the day Final Fantasy was considered an RPG
However things have changed: video games have evolved since then and now games like FF are called JRPGs. Part of the reason why this has come to pass is that games like Fallout, Baldur's Gate and Never Winter Nights have shown what an actual role-playing video game should be like (and there is still a long way to go for a true RPG)
An RPG isn't defined by it's setting, it's defined by it's mechanics: Diablo is a game where you go around killing everything that moves and where you make no decisions. It's an action game with a few elements that have been traditionnaly associated with RPGs (character progress and equipment): that doesn't make it an RPG, it just has RPG elements.
Compare a game like Fallout New Vegas to Diablo and tell me which one is an RPG.
Now this isn't meant to be some intense debate on my end (not angry or anything, I like participating in these discussions during down time at work), I just don't think that, with how video games are TODAY, that calling a game like Diablo an RPG would be correct. When Diablo 1 came out in 1996 maybe but not anymore.