To clarify, if I was introducing someone to the Diablo series for the first time and told them they’d have to start on the first one. I wouldn’t want them playing the bare vanilla version. There is a Bezelbub mod out there that gives the game lots of QoL improvements, you’d be thinking you’re playing a build of Diablo 2 before its final version.
So, if I had to tell anyone what the best way to play that game would be, it is the Bezelbub mod. That was how I’ve beaten the first game anyways.
The first Kingdom Come: Deliverance was a great game and I think it should be played first, but I understand it’s old clunky and unoptimized. These days it should be played with certain QoL mods like unlimited saving, instant herb picking (no animation), richer merchants, and trough washing deluxe/clean Henry (honestly I don’t want to spend all my time going to the baths or looking shite). There are others, probably about 7-8 total, that I recommend but you get the idea.