Come on man, don't leave us hanging! Tell us what you loved most about it, and what you miss from it that you haven't been able to find in newer editions. Turn that nostalgia dial up to 11 and let us have it.
LOL, what is there to say?
I was only 5 when I rolled up my first AD&D character in 1979. A Magic-User named, "Dartson" because he threw darts, he later evolved to become "Darson" and I used to have a letter from E. Gary Gygax when I wrote to him about maybe featuring the character in a module back in 1986 or so. I
SO wish I still had it!
The game was complex, had lots of rules, but you didn't have to use nearly all of them because we were used to the simpler Basic system. Advanced offered more if you want it. Building adventures are pretty easy compared to the balancing act of 5E IMO.
The characters were simple, with only certain things available. Most of what your character did was about the choices you made
in the adventure not after you leveled. I sometimes hear people complain, "But I couldn't play this or that!" and I respond you can play pretty much anything as long as the DM approves. All concepts were achievable without having to make subclasses for each and every one of them. How was this possible? You just played your character that way. What you did
with your character was vastly more important than what your character
could do.
In our modern era, some things aren't very PC. Well, I am all for certain changes from 30+ years ago, but some things and changes I don't like. AD&D had certain restrictions and limitations because they made sense. Sorry to the people who didn't like them, but I did. There were more that weren't there, but should have been even.
Of course it was the edition I grew up on and for that alone I have fond memories. Hundreds of adventures, thousands of hours of play, dozens and dozens of great friends; not to mention the education it gave me. I learned a lot about math, economies, statistics, and other areas that aren't as prevalent in D&D nowadays IME.
Finally, I only had about 2-3 pages of house-rules for AD&D, compared to the 16 or so pages our group has for 5E.