I'm two evenings into a D1 (DevilutionX) single player story run though. Can confirm. Definitely much slower and more deliberate, and not just because they hadn't invented running yet. Nothing respawns, the world is fixed from the start, so everything is a limited resource. Do I really need to buy this sword now or should I try to hold out for something to drop? Much more strategic gameplay... Slow forward exploration, hiding behind doors and corners letting monsters come to you one by one, stuff like that.
In the later games I'd just whirlwind through everything (spin2win, baby!) and hope for the best. If I need more gold or whatever I can always just save and exit and come back in and run through the area one more time. Definitely not doing that here. Every choice matters, so slow down and make it count.
Shit, you're right, I forgot all about that, it'd been so long since I've played it. Starting a new game with an existing character keeps your stats/inventory but resets the rest of the world.
I guess I'll go ahead and buy that sword now.