It's not aesthetics for me as much as sufficiently older movies are a lot closer to stage plays in how they're filmed and storyboarded, and I generally dislike plays and musicals whatever the content is (case in point: I don't have any interest in Hamilton nor Disney movies). Then comes a lot of older movies having pacing that doesn't fit the time and mental energy commitment I am capable of making.
I can appreciate classics like Lawrence of Arabia, Dr. Zhivago, and the Deer Hunter, but I generally don't have 3+ contiguous hours to do anything anymore let alone watch a movie and I feel ashamed I can't honor such works with a proper, conscious viewing either. For "pop" arthouse movies closer to something like Begotten or Valhalla Rising, the effort to get value is even worse because I am not understanding what the symbols are and it becomes more of an exercise in "let's analyze scenes!" than "let's watch a movie to stimulate our minds." Some people don't like video games for similar reasons I feel - they want passive, decision-free entertainment.
It's probably different to different people, but I'm having trouble with old movies for a similar reason - they feel too slow to me. The plot doesn't develop fast enough; sometimes I actually can't make heads or tails of it, because some events are spaced out in a way that breaks the casual relationship in my mind.
The what it differs from what you described is that I don't mind active, decision-rich entertainment. I love video games. I just have too short of an attention span to really enjoy old, slow-paced movies :/.
To me, it goes so much further than just something like the HD.
It looks old the same way an old photograph looks old. The colors are all off: The jokes aged. The sound seems weird. The special effects - even if they were amazing at the time - were off. The movies were obviously made for a different time.
Granted, there are exceptions - a few movies age well, but the vast majority do not.
I agree with your last sentence but there usually is a reason a classic is a classic. Same applies to literature.
However if there is one thing I have learned is that everyone has different tastes. My wife cannot watch any film made before she was born while my golden age of film is about 1940 to 1970. I will take All About Eve, Double Indemnity, the Thin Man, and anything with Humphrey Bogart over anything released these days. That is not even getting into classic foreign films.
A key component of classic films is that they weren't able to distract special effects, or even colors for some, so plot was that much more important. I can't imagine that mumblecore will survive the test of time but I could be wrong.
I can appreciate classics like Lawrence of Arabia, Dr. Zhivago, and the Deer Hunter, but I generally don't have 3+ contiguous hours to do anything anymore let alone watch a movie and I feel ashamed I can't honor such works with a proper, conscious viewing either. For "pop" arthouse movies closer to something like Begotten or Valhalla Rising, the effort to get value is even worse because I am not understanding what the symbols are and it becomes more of an exercise in "let's analyze scenes!" than "let's watch a movie to stimulate our minds." Some people don't like video games for similar reasons I feel - they want passive, decision-free entertainment.