Before you grab the pitchforks, let me explain a bit.

For one, Preboot!SS is super nostalgic for me. It's what I grew up with. Histrousle 3.0 was like the theme song of my childhood. If nothing else it'll always have a special place in my heart for that alone.

Second of all, it's fun. Reboot!SS is very well-written and pretty unique, but like... it's hard to read, for the same reason Steven Universe Future is hard to watch. It's really fucking dour. Depressing. Downbeat. Unhappy. It's a world that's gone to shit where everyone is really fucking sad. And there are good reasons for it, it's great storytelling, but it's hard. Preboot? Not at all. Upbeat, goofy-silly like the original Undertale, has a sense of whimsy. Occasionally gets dark, but when it does, it's really well-written and makes sense. The character swaps are logical and are written exactly how they should be. Sure, it's a lot like base game UT, but that's pleasant. It's a relaxing and reassuring thing to experience. It's what AUs used to be- Undertale, but somewhat different, for fun, rather than a whole-ass new thing with sort of the same characters kind of that has to be the craziest thing on the planet. Let me have those simple times back. Not every AU has to have an anime plot, dude. Simple things can be fun.