I tapped out @ D3 saw the writing on the walls, Played with a few buds, had fun finding treasure goblins and calling everyone into the game and the unicorn level instead of secret cows was a fun experience. That said, was only playing to trade. Didn't buy D4, the screens looked horrible and Blizzard doesn't support their games with updates like the competitor was doing (grinding gear games path of exile). That having also been said the trade values in POE drop lightning fast in recent leagues - not really reminiscent of the 3 chaos orbs per exalt you would see in the games beta state before release. I haven't played D4, sat this one out as I don't think Blizzard is trying to create the best games, I did play and trade Diablo 2 resurrected to some satisfaction.
I remember one Diablo 2 patch coming out like 1.5 years after blizzard announced it and they just started saying things were done when they were done, lost some years to WoW: who didn't. Todays blizzard is not really a company I support. To me its no longer competitive but I'd imagine their releases still trade well given the fanbase and how many play the games.
D5 would not attract me, the company doesn't service me as a player, sort of lost interest but I can see people who play just to trade and service those who do enjoy playing.
For traders I think Blizzard could remain relevant but it sort of seems like the company tries to under-deliver on purpose.
Games I've done more recently include tarkov but I didn't trade it, just played for fun - although the amount of hackers/radar kinda blows.
Always an enjoyer of economy and trade oriented games.
I don't really care to yuck others yum in this regard and its popular to hate on blizzard - which almost makes the practice passe - which also makes it lame and a goofy fake sided argument because you either enjoy lower quality offerings and are blinded by the magic or you dislike it and cannot find yourself enjoying the games and its an exercise in futility to convince the other. I think Blizzard is historically good for trading on new releases and it will probably still attract avid JSPers looking to play and trade a game.
All this said, if you traded as a career instead of a hobby (never been there), I think D4 / D5 is a bad game to play unless you properly claim and do your paperwork because your uncle sam is very interested in Blizzards economics and data.