Just because you think Undertale is mediocre doesn't mean that the majority agrees with that sentiment
Undertale was only an alright game IMO, nothing too special or amazing, but Deltarune is only the first chapter of a much bigger story that shows improvements over the first game with it's UI, better and more fluid sprite work, and still very enjoyable soundtrack
So there's definitely a reason to think it'll be something better than it's predecessor
Basically, just let people enjoy a thing, the BLF goes through avatar phases all the time, and two threads on the same thing isn't spam, it's unnecessary as i've previously stated, but it's not spam
You guys are just making a mountain out of a molehill just because it's something you don't like