Newer Pokémon games have way more quality-of-life such as EXP share and way faster animations so it's not a slog anymore. Recently finished Scarlet and enjoyed it very much. Currently replaying SoulSilver and I couldn't play it without cheats that make the game a bit faster (cutting repetitive animations, making the game run at 60 FPS, etc.) since everything is so slow.

I'm nearing 30 and have played a lot of JRPGs in my life.

I completely agree with this. I'm playing through Leaf Green, and I'm around 8 hours in with just a single badge. I don't think I'd get through it without the boost of nostalgia for the GBC/GBA games. The newest games are nothing like the slog we went through as kids.