I feel you, I don't have a lot of time either - more than that, but not a huge amount. That's why I prefer having more viable builds. I could play Path of Exile, for example, but I don't want to spend hours trying to learn how to even play the game this particular season so that I can make a character that won't be a giant ball of crap. If there's more build diversity, you're more likely to do okay just doing whatever you want to do, without needing to research builds ahead of time.

D3 has builds that are far superior to everything else, but I don't think D4 is any better - nerfs mid-cycle or not. Using a bad build is punished less in D4, but you're still going to be on struggle street if you pick a shitty build. With D3 and D4 if what you want to do doesn't just happen to be one of the good builds your character is gonna suck. It matters less in those games though, since gear is absurdly easy to get in D3, and respeccing is fairly accessible in both games.

In fairness to your point though, back when D3 was new and its hardest difficulty was borderline impossible, I found a mage build that could do it, and when I had finally gotten the gear I needed (NOT easy back then) it got nerfed the same day I was able to use it. That was super frustrating. I would argue they did that to help push the real money auction house though, not promote build diversity - don't need to buy gear if there's a class that doesn't need you to. That's the cynic in me I suppose.