I didn't grow up with Super Mario Kart, I got into the series with the more modern games (specifically, Double Dash!!) and am only now going back to play the older games in the series. Speaking of that, I own all of them except for Mario Kart 64, and the $60 DLC pack known as Mario Kart 8 Deluxe.
Everything is absolutely fine up until 100cc Special Cup. The tracks are too narrow, the other racers' sprites are too big, and they drive right in the middle of the track. It also seems like just about anyone is capable of knocking you clear off the track, regardless of weight. Also, can we talk about the handling? It sucks. When you push a direction, half of the time you slide in the opposite direction instead. It makes it very difficult to stay on the track. A fair amount of time, neutral hopping can stop this from happening, but it's a gamble.
I loathe the coin mechanic in the older Mario Kart games. In the newer ones (7 and 8) it's not as bad (they're pretty much just a really grindy kart part unlock mechanic), but here the coins tend to be out of the way, where you'd never want to actually drive your kart, and they have very small and precise hitboxes, which makes them incredibly difficult to pick up. This wouldn't matter if your speed, number of retries, and ability to not spin out when something hits you wasn't dependent on you picking them up.
Also, the walls are terrible. If you hit one, you might as well start over, because otherwise you're going to 8th place and there's no real way to make up the positions you lost. "Just use powerups!", you say. Yeah, I tried that. I'm tired of getting bananas and green shells in 8th place. Even the lightning, which is designed to let backmarkers catch up, isn't terribly useful because when it ends they all just barge their way past you again. Red shells are almost pointless as when it doesn't just slam into the nearest wall, the CPU players have a tendency to jump them. It's like there's a distance-based sweet spot where red shells actually function properly. Also, the star doesn't last nearly long enough and ends instantly if you hit certain hazards that it sometimes auto-jumps you over.
Speaking of hazards, the very first track in 100cc Special Cup has the stupid bridges. The first one is fine because it's pretty easy to hop the broken bit or go to the left of it. The second one however, you either need to hop the gap, or be going fast enough to just sort of skid right over it. However, the game just eats your input most of the time when you try to hop over the gap, so 90% of the time I end up in the water when I reach this part of the lap. And when you're in the water, you go incredibly slowly, so by the time I'm back out of it, I'm in 8th place, from which there is no recovery. After the bridges come the moles. Even if you think you've avoided them, sometimes a mole will just fly at you from a mile away. They instantly halt your momentum and you have to spam left/right to get them off.
If I could start the first track of 100cc Special Cup in first or second place, I might have a chance. But you have to start it in 8th, which means having to navigate the other racers at the beginning and lose all your coins getting bumped around by them. It's not exactly fun, and a lot of the time when I decide to try again at 100cc Special Cup, I spend my time doing the start and the first couple of corners, getting knocked off the course, and resetting. Eventually I either give up and turn the game off or there's something else in life that I need to do.
No wonder all the speedrunners race time trials. Time trials eliminate a lot of the bullshit this game is constantly flinging your way.
Related: If you want the classic Mario Kart experience, Mario Kart Super Circuit is an excellent game.
