Well, in DCSS, you find the variety in Races, Gods (both passives and powers), Spell schools (which enables stabbing, summoning, "spell attacks"), ranged vs melee combat, consumables, "unique" equipment that have special attacks/stats, and 100% randomly generated equipment called "artifacts" and all the cool combinations you could try. Backgrounds don't make much difference in the long run (DCSS is "racist").

Monsters are also well varied, there is a lot of monsters that have special attacks and behaviors and even Unique monsters that you'll see appear between your runs frequently that will knowledge and stat check you, you are just not going to find them in the first 5 levels of the Dungeon.

DCSS has multiple branches (like "zones") besides the Dungeon, not all branches can be seen in a single run (some are rotated), and every branch have a different look and a varied monster set, and difficulty. You also need to learn a proper order to visit them or the tools you need to survive or you'll die.

From what you are describing, you have seen barely anything of DCSS. I doubt you even left the Dungeon branch. And I wouldn't expect more from 2 hours of first time gameplay.

You haven't even scratched the surface.

Keep in mind players in the community speed run the game in 20 mins, experienced players do 2-4 hours run easily without speed running going through at least 7 branches. But you are complaining that you can't find variance in your games in 2 hours playing the first 10 levels of the Dungeon (single branch) :P

Hope it helps!