This is literally all in your head. I'm in my mid-40s, started with the original Diablo, hated the trading dynamics in D2 in particular, and have made fairly extensive posts about how little I think trading contributes in value to the game. The one pro-trading argument that I think holds merit was I think Edge's, when he talked about swapping gear between friends, to boost a friend or give them a super rare drop their main can use. I see value there, but don't play with a bunch of friends myself, so that value's pretty dependent on the user. Most of the trading didn't take that form, though, it was advertised auctioning/selling gear, whether for in-game currencies or real cash through third-party systems. And that's the kind of trading that I don't see any value to. For such trading to have value, drop rates need to be lowered such that it's difficult to get items worth trading, to encourage people to trade for them, and that hurts those who don't want to engage in trading. It creates really negative community dynamics and encourages exploitation and abuse in a lot of petty ways. And I don't see scanning auction houses or external forums hunting for needed gear or price-comparing between vendors to be productive and engaging gameplay.
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I hope for the same, but it bears pointing out that rifts were a significant upgrade in terms of endgame over D2. They're at least fairly variable and there's some unique iterations that pop up. D2 had a few super-bosses, but mostly you were grinding certain levels over and over again to get loot drops; I still remember whipping around the Cow Level with a Javazon barely seeing anything die because lightning was killing everything for a screen-and-a-half's radius around me, as fast as I could run and throw, over and over, or grinding Mephisto over and over.
D3's also got a better difficulty scaling system.
D3's endgame is only okay in modern terms, but it was still a big improvement overall.