My cousin has had the same reaction when showing anything he liked as a kid to his kids. I believe things like pacing, dialog, time-era and camera work are something that they can't get over. I remember a time when I couldn't stand Westerns, 60/70s movies and anything that was monochrome. Then, about high school age I started really enjoying cinema and animation. I watch even the worst of B-cinema movies with joy.

In the end, I felt this way about cowboy movies because I couldn't relate to the time/age depicted. It felt like a long long time ago that I didn't understand or want to. I believe today's kids feel the same way. No smartphone? No computers? Ancient tube TVs? People meeting up and talking instead of using discord or whatever? I can see why today's kids just don't enjoy the movies of 30+ years ago. The time presented in the movies is completely foreign to them despite it being no so long ago but in reality, culturally, it was long ago.