so you really think someone gives a fuck about you cursing

You know, saying that Hearthstone killed CCG is the same as saying that WoW killed MMO. I mean, it's true that both games took genre in certain direction, but if some playres who played other MMO/CCG abandoned their games that's because those games were not as good as they should be. Otherwise why would they went to other games or why other players went to other games instead, you know Everquest or Ultima?

Yep it really seems like a vicious circle sadly, but I don't think that that means there will always only be 1 or 2 kings of the genre with comparatively simple mechanics. Hearthstone could've been a good deal more complex and I think it would still have been as popular. It's everything else it got so right that needs to be highlighted to the next developer who wants to create an interesting card game with a large following. Or from the other direction, how to address those 4 concerns a Hearthstone player might have going to another card game. And as a bonus, to distinguish a new game from Hearthstone, perhaps it's likely that it would be more complex and interesting.

But I must confess I don't see this working for a new IP. You need to start with something that already has a large appeal, otherwise you won't grab the interest of, I would imagine, the majority of Hearthstone type players with only a semi-casual interest in the genre itself.
Still, that leaves several IPs which could make for a damned fine collectible card game if given a proper development team : warhammer, warhammer 40k, lord of the rings, star wars, battletech. Hell even Disney! I think you could make an amazing card game with Disney characters, with dlc-expansions based around movies/tv shows.
And that's the other thing, I felt the money spent on those dlc-expansion things of Hearthstone as well worth it, in large because of the awesome associated single player element, even though I detest mini-dlcs in other games. So I'd think that creating a proper collectible card game should be a quite the financial incentive for people with access to large established IPs.

I know you'll hate it :) but you should check out Fox's butchering of a very good premise of a card game with Animation Throwdown. Notice in particular the excellent production values, and how cards combine to create a different card from the particular show (think a PPC weapon card combining with a Timberwolf mech card in a battletech card game). I mean it's a splendid base concept, regrettably butchered into a kindergarten-level game :(
That's the only real worry then unfortunately. Why go all out and create something amazing with your massive IP when you can just create a silly kiddie game for some easy cash where the players don't actually even play against each other.
We have to hope that a developer goes in with the mindset of making a Hearthstone killer.

So this was about online card games, and whether Gwent is dead or reinvigorated? Or maybe even both, like an undead zombie?

That's the thing about online games, popularity means even more popularity because online games become meaningless if there are no other human players, no matter how good you otherwise think the game might be. That's the reason I moved from Quake TeamFortress => TeamFortress Classic => TeamFortress 2: because practically everyone else did too.

Another thing that applies at least to me that when I find an online game I like (and which has enough players), I usually have no reason to look for alternatives. I keep playing that same game over and over and over and over and over again. This just strengthens the effect that popular games tend to remain popular.

Or I dunno, there must be a reason why people still occasionally abandon some games in order to move to some other. Maybe people do eventually become bored with the same old same old, and start looking for the next big thing, eventually.

And one reason I eventually abandoned Quake TeamFortress because cheaters started running around in the game uninhibited, without no one trying to effectively stop them anymore. I recall it was "Punkbuster" that was used in QTF to try to stop the cheaters, but apparently it wasn't that effective anymore.

With single-player games, I more switch between games, move to new games, try completely new games etc.

Great topic mate! Also I like the way you use a "q" instead of "c" to spell words as in "qould", Very classy. Although I would suggest "quould". There should be more of it.