I still recommend playing vanilla for first time, but switch to GMDX for consecutive playthroughs. I think the kind of clunkiness zoomers complain about isn't the kind of polished changes GMDX provides, but inherent gameplay philosophies... like waiting for the reticle to become smaller at low level, having to traverse big maps without much of an indication what to do, how to discern they're being hidden without a piece of HUD indicating them so... these things filter and will keep on filtering retards. And that should be a good thing.
You underestimate the scope of Deus Ex's clunkyness. It took me decades and much analysis to see the full picture. Let me give you some examples. There is probably about 250 such clear-cut fixes in GMDX, but we'll go with 10:
1. Stepping on approximately half of the game's actors would throw you around like a pinata, you can't move until the physics engine gives you back control. Even a pillow or a rat.
2. Scope toggle was tied to rate of fire. If you used a weapon with a slow rate of fire, such as a sniper rifle, you could not toggle the scope on or off for approximately 2.5 seconds after a shot. As you can imagine, this arbitrary restriction is clunky asf and serves no functional purpose, it's just an error in execution.
3. When using the mousewheel, whenever you would scroll the toolbelt, then go to do so again later after say unequipping a weapon with a right click, it would "forget" your current positioning. This is mathematically suboptimal to always reset you to the first belt slot.
4. tiny objects on the floor would be considered something for NPCs to navigate around, resulting in frequent running into walls (among many other things causing terrible pathfinding).
5. Over half of the skills are outright robbery or non-functional. There's the swimming meme everybody knows but it's more like half of the skills when you have the full picture.
6. any time you want to interact with anything in the inventory, you have to click tiny use/drop red buttons. GMDX adds inventory shortcuts, which cuts inventory time by 2/3rds.
7. For stealth takedowns to register you pretty much must be touching the victim from behind, which is counter intuitive as bumping someone from behind by moving into them would alert them: 32 unreal units tolerance, which is very strict especially when they're moving away from you and resulted in frquent WTF moments. Furthermore, you have to aim for the torso. Hitting the back of the head would
not result in a takedown, especially with the baton (x2 damage, as opposed to x12 damage of a takedown).
8. The silencer mod doesn't actually do much of anything at all. All unsilenced weapons that can be silenced only made a tiny amount of sound around the player, we're talking around 8-10ft or something like that. You could be in a small-ish room with an unsuspecting NPC, fire your weapon at him and miss, and he would not notice. Ergo, all silenceable weapons practically have silencers by default, it barely made a difference. Edit: this isn't a "clunkiness" example, more something obscure and learnt by paying very close attention, like say, when testing things when programming a mod. Oh well. Still important
9. whenever you got poisoned, whatever would be held in your hand would disappear, then magically reappear into existence.
10. You can't move a corpse until you loot all their stuff. In GMDX, simply double click.
Deus Ex is probably the most flawed notable professional release of all time. Nothing else quite comes to mind, but of course nothing else really has its design scope either.
My suggestion to you would be to go back and play vanilla with the fresh perspective of GMDX's polish.
Edit: Morrowind and VTMB could have Deus Ex beat. Maybe. But Deus Ex has superior core design to them and thus deserves better.
