@Retreater @Jmarso having started playing in 2e, I can share a lot of your observations.
Nostalgia surely plays a huge part, but it's not just that.
I think the most important aspects that were lost during the evolution between 2e to 5e are:
- magic is magic. Magic users were fearsome because they could stack up immense amounts of bonuses and make them nigh invincible. This also reflected in the campaign setting itself, with counter magic and special tactics being part of a plausible world. From a gaming point of view, this can of course get out of hand very quickly, especially today that people play through a VTT instead of in person, and a DM may not even know who the other players are, thus the mutual trust at the table can be very low and the potential for rule abuse very high. So here we are with systems where magic has to be controlled (too) tighty. Enter concentration, and saves at every round.
- most monsters are just for grindind. One of the very interesting aspects of old monsters were their abilities to inflict conditions that were lasting (aging, diseases, death even just on sight), and the encounters with them were scary even if few hp were lost. An encounter with a wight was dreadful because you were probably going to lose a level! Losing a character due to a faild single roll sucks, though, so I can understand the rationale of removing all save or die effects and rerolling saves more often, but now those "dreadful" monsters are way less scary.
EDIT: I'm still reading the Monstrous Managerie, but after this post I read LU's version of the Wight, and it perfectly captures the old school feeling of the monster. They really did a superb job with this manual. It should completely replace any Wotc attempt to 5e monsters.
- Also, monsters could easily be immune to normal weapons and even magic weapons, requiring at least a +2 or even +3 weapon to be hit. This did cause inflation, in a sense, but also made it so that they were very dangerous even for high level PCs, if not properly equipped.
On the flip side, 2e was riddled with terrible and inconsistent mechanics, tables which required a lot of page flipping, weird and often missing balance, etc, so I do honestly think that the mechanics are so much better now. It's just that some of the "feel" was lost, and it may be recovered in a smart way IMO.