They didn’t elabortate. It doesn’t matter, though. Mythic dungeons should have it’s own gear. You should not get mythic raiding gear if you can’t complete mythic raiding content. Period.
But do you actually believe that this is “everything wrong with BFA?” If so, you must have a pretty high opinion of BFA, I think there’s a lot more that could be improved.
The mistake you are making, OP, shared in tandem with the poster you are quoting, lies in associating any specific ilevel of gear exclusively with mythic raiding.
Having various methods by which to acquire good gear is actually a GOOD thing for the game, and draws far more people in than it alienates.
If you can come to terms with it on this level, I promise you your stomach will settle right down.
As a raider, I would say he gets his gear from Mythic+ running. As someone who raids and does Mythic+, I will say if he is running Mythic+10s to get his gear and never steps into a raid more power to him. Mythic +10 and beyond is no joke and requires just as much skill as raiding.
That’s why I’m asking. Are you just believing his claim that he’s geared for it without him actually doing it? Or did you look at his profile to see what content he’s actually done? And is the gear he’s wearing optimized well for raiding? Or does it just have the high Ilvl with stats all over the place?
In my frost gear I am item level 389 and I’m 390 in my fire gear (yes, I have two sets) I have six ilevel 400 pieces and I have only done one raid, Uldir normal 2/8. I’ve done one key (5) and I’ve done one LFR.