I'm not into SE's koolaid to accept "what they've got" for an answer. The dev team has been very visibly slowing down ever since Heavensward despite all the fantasiabux and new sales. If they have to scramble resources around just to get something, at all, out of the door, isn't that exactly THE problem? Because Stormblood wasn't exactly a stellar start already, formulaic rehash of HW leveling campaign, but with subtly worse zones, questionable class playability with feedback outright ignored - as if 1.x period taught them absolutely nothing, that any kind of QoL change gets put into a huge queue of "maybe we'll get around to it once we can spare one of our three programmers" or that they have to beg for effects artists on celebration stream is super, super worrying. Game health huh?
Super Savage is gonna be good for me, you, and maybe the rest of the 3% population, but as an enduring kind of content, probably not.
4.0 needs something to hook people to stay now. Not by the New Year, now. I already see people dropping off like flies, and that's raiders who've invested more time and emotion into the game than people who just go through leveling campaign and doze off.
I don't know why you keep fighting the strawman, Nobody is seriously saying "Oh no, not the dungeons, I loved them so much" (although like I've said many times before - SE's dungeon design is lazy garbage and they could've done so much more but gg on that now I suppose).
The issue is that they're not increasing the variety of stuff there is to do. Not visibly so. There's no new content coming. A PVP nobody's gonna play made our of reused assets. One raid fight made out of reuse assets. A linear, easy as bricks LFR raid. Probably another couple mob grinders in form of Diadem 3 and PotD 2 down the road. Is that what they meant by new content? Or are players supposed to wait until late 2018 to actually see new things they promised to do in the expansion?