Several things.
First, YES, as THACO was written, it WAS superior for the style of play I enjoy. In life, people don't advance at the same rate, and those who train in certain areas are better than in other areas. 2e simplified the THACO equations so fighters advanced in their bonus to hit at a 1/1 level ratio. Rogues at a 1/2 ratio. Priests at a 2/3 ratio, and Mages at a 1/3 ratio.
I never had a problem with subtraction, which is all THACO really devolved to (and it really is kind of sad how many new comers think subtraction is really hard...they should try calculus sometime, or business stats and trigonometry which are things I used to do on a daily basis before retirement!).
The idea that you can have your dexterity be useful no matter what you wear (Rather than the idea that plate is so heavy that you can't move in it) is another application to AC (and hence THACO) that I prefer.
So, yes, THACO AND more to the point, HOW each class was differentiated by that is a major point. Now if 5e had a similar system where it differentiated the proficiency bonus dependant on the class...my opinion may be different. However, I think class differences in that are important. It would be possible for 5e to actually apply these things in it's rulesets, and if it did, this idea of playstyle superiority of 2e would vanish most likely, but as 5e does NOT do this...for the playstyle I enjoy the most...2e's THACO system is superior.
In regards to skills, you can see a HIGHER differentiation in 5e (at least with Rogues and Bards) in that same degree. In that light, I probably would agree 5e has a superior idea in regards to skills, at least to a point.
However, the idea that a Rogue could try to move quietly, and then if they fail that, have ANOTHER shot at moving silently, or try to move silently and if they fail, roll like everyone else to move quietly...that type of two tier system of skills IS NOT in 5e and NOT really replicable in 5e. It wasn't used by everyone in 2e, but that it could be, and make the rogue actually have rogue skills that were pertinent and unique ONLY to the Rogue (whilst having the same abilities as others, basically having a second chance to succeed if one wanted to use the rules that way) made the usefulness of skills for the Rogue and Bard (and Rangers) better for stealth and other subterfuge based skills.
I actually like the way 2e handled abilities. I LIKE Constitution and Strength (exceptional) being the realm of Warriors and having that special chance to get that high applicable to them.
I also like that most likely, that wasn't going to happen. That you could have stats that gave you NO bonuses and still be a normal adventurer that had a chance of success. There was no race to the top of the abilities ladder like there is in 3e -5e.
On the otherhand, I think 3e and even 5e handle the idea of saving throws in a better and simpler manner. It's far easier to remember what your saves are and apply them then the earlier system of 2e.
However, I liked how 2e emphasized the differences between creatures. A Wolf is NOT a human...and their minds work so differently as that there really is no way for them to be the same things. A wolf can never be a doctor...but a human will never be the pack hunter that can run as quick or bite as efficiently as a wolf. They are very separate creatures.
In the same light, 2e had that same dynamic of differences between monsters (such as goblins, gnolls, wolves, bears, ogres...etc) and humans. These differences even were applied to races...though the races were more intelligent and hence had some similarities to humans...those differences were also very marked. This was the excuse of why races had racial level limits...because you had a race trying to act human in attaining human classes. They were more skilled in some areas, but others they were not...because they were VERY different things then men.
In that same light, I also like the way you could multiclass (but if it went high level, you'd eventually pay one of the costs of that multiclassing) and advance in several classes at the same time.
So, there are things that I really like about 2e (but I can't say I really miss them. If I want to play 2e I still have the books and can still get a group together to play it if I want...so that's more a decision of whether to play 2e or not).
I think there are some things that 2e did better than 5e IN MY OPINION, but at the same time, I think there are many things 5e does that are superior to 2e (for example, as I notated about skills in general above and saves...but there's more as well...such as simplicity of rules in 5e comparatively to 2e if you really think about it).
I don't think it's necessarily nostalgia, but rather which way you prefer to game, and which types of rules and restrictions you enjoy in your games.