I'm late to the thread but my 5p
I'm not someone who owns lots of bikes or has a high bike turnover but I do own one old (mid 80s) and one new (2012) one.
The only thing that bugged me about the old bike was the narrow dropouts that limited my options with when choosing modern hubs and wheels for lower gearing. I say "bugged" because it no longer bugs me because I fixed the problem by cold setting (=bending) the frame.
I'm perfectly happy with with the rest of it. I've never ridden a bike with disc brakes, and what you've never had, you don't miss. I'm entirely happy with non-indexed gears. I can get 30mm tyres on it (without mudguards). I wouldn't know a thru axle if it bit me on the bum.
I'm not knocking these things, I'm sure disc brakes are great but I've just never tried them. I have indexed gears on my modern bike and they're OK. (Actually they aren't OK at the moment as they were a bit wonky on my last ride, but I'll sort that out)