Ocarina of Time speedrunning has gotten to a really weird place now, where they basically set the character's name to a string of bytes which are executable code, and then de-reference a pointer to it and warp directly to the end credits, all within a few minutes of gaining control of Link. But, the community has a whole bunch of categories for different types of runs, from ones that are basically the Any% category before SRM (stale reference manipulation), to semi-legitimately beating all the dungeons (though with lots of sequence-breaking), to fully glitchless. It's a lot of fun watching some of those other-category runs for a taste of "normal" gameplay done at a very high level.
Another thing that's fun to watch runs of is randomizers (chest contents, quest rewards, sometimes even doors), since then you're not just seeing high level play, you're also seeing someone doing the live work of reasoning about their route through familiar-but-scrambled territory:
OoT speedrunning is very unique, and since it was a game I played a lot as a kid I'm always excited to watch the ways it's beaten.
I do admit I prefer the categories that emphasize more gameplay though, even if the glitches are incredible.
I'm really fascinated by speedrunners who can beat my favorite classic games less than an hour, sometimes in minutes. Some of that is cutting weird corners but often it's pure excellent execution.
I often wonder about doing that myself, playing hundreds of hours of a single game to master it. Putting all of my focus on a single game like I used to as a kid, but I don't find anything keeps my attention that way now.
I think partially it's what you said, more money than time and I naturally gravitate towards spending my time on novelty instead of mastery. That's just how my brain works.
The other piece is when I look back, I don't think I spend nearly as much time replaying the same things in the past as I feel like I did. I think those memories of playing and replaying games are somewhat distorted by my memories.
I also spent a great deal of time watching those games being played by friends and their siblings and so forth, during sleepovers and after school.