As far as I remember, the first game was less restrictive, because numbers mattered less. There was no armor, so even higher leveled enemies could in general be outplayed with CC and enviromental effects like smoke wall or electrified water. (Noone really cares about electrified water or burning oil as long he has enough magic armor left.) Also the stat bloat from leveling was not has harsh as it seems to be in this game.
Boss fights like Bracchus or the Doomrobot and the spider desert with perma debuff were the only regions I remember, were you had to prepare that much before entering, as far as I remember. Also there was rarely a harsh cut between acts, so you could always just walk around an explore to get on that way exp or better stuff (with sneaking or going invis at least).
One of the reason why DOS2 is less open and more restrictive compared to the first game.
Though it has been a while since I played the first, so my memory is probably a bit flawed.
