"Aged extremely well"
The controls sure as hell haven't. I understand they're working with the limitations that come with character movement on the keyboard, and that using controllers on PC wasn't really a thing back then (since the freedom of movement offered by thumbsticks works better than keys), but they really didn't need to shoehorn an extra movement speed and key binding in there. Splinter Cell did a much better job of it, using the scroll wheel to allow you to adjust your character movement almost seamlessly, and I know scroll wheels existed at the time.
They may has well have made being spotted an instant game over too, because the combat is so flawed, I know it's not a game about combat, but sometimes you just can't help being spotted. They teach you all this sword combat in the training, and then when you actually get into the game it amounts to mashing left click on a guy for like 30 seconds before he drops dead, it takes forever to kill a single guy. The enemies can outrun you too, since your fastest movement speed is a fast walk, so hiding is basically a no go. I understand that being caught is supposed to be a punishing and difficult thing, but in thief it feels like artificial difficulty, it's not a hearty challenge when you get caught, it's just flat out unfair. When I get caught I just revert to last save, because trying to escape or kill the guy is too much of a pain in the ass to bother.
The guards can spot you stupidly fast as well, and seem to have superhuman hearing, being able to hear me floors below them, or through walls, or whatever, and have instantly spotted me from a distance.
The controls are fine if you're not a console peasant that can't comprehend more than 6 buttons. Sure, the speed system in SC was awesome, but it doesn't make or break the game. Thief was built around its control system and it works. Maybe if you complained about the inventory system, then I could agree with you. Your problem with Thief is the same problem test audiences had. These people didn't like a game that was a challenge. Nowadays, retard gamers can't lose in a game, because they want to have "fun". That's why you have "Press x to kill these 5 dudes" in new SC games. That's why the new Metal Gear has slo-mo when somebody spots you. Thief is a stealth game. You're a thief and the point of that is that you can't go in guns blazing (although if you're good you can circle-strafe everyone to death). Complaining about that is like complaining that you drank hot water and burned you throat (I guess that's why you Americans have "Food is hot" warning labels)
Also: "controllers are more precise". Buehehehehe.
"Zipping from cover to cover"
What does that even mean in this case? You take cover in Thief as well. Hiding behind something, like the corner of a wall, is cover. It doesn't make much of a difference if newer games have cover systems, because they both serve basically the same purpose, and you're still doing the same thing. Most first person games (like Dishonored), don't have cover systems either.
What I'm saying is modern stealth has two states: either you're invisible, or eveyone knows where you are. Modern SC games have a cover system that lets you silently swoop between cover (so does the new Thi4f). Dishonored also has the lean system where you're invisible no matter what. It's easy mode for console babbies.
Again, like cover, this doesn't make a difference. Sneaking up behind a guy in like... Splinter Cell or whatever, and getting a really quick little animation of Sam choking the guy out isn't any different from walking up behind a guy in Thief with the club and clonking him on the back of the head.
Neither of those are cinematic takedowns. In modern stealth games you have a "Press x to do an awesome animation killing all your opponents". Sneaking up on a guy and grabbing him/bopping on the head in Thief or old SC requires patience and actual input.
You should play Mark of the Ninja. Easily puts all other modern stealth games to shame.
Because modern stealth games are shit. Also has nothing to do with Thief
Ah, you edited your post in the meantime. I'll agree with you on the zombies. It's one of the reasons that it's Thief 2 that is the perfect stealth game (not "action-stealth") and not Thief 1.