It's a subpar bullet hell game with a generic "my friends are my power!" story.
Eh, you're not wrong, but I find that the general atmosphere of the game more than makes up for its shortcomings. Personally, I quite liked it
I liked the game, but hilariously saying it's the greatest game of the century is irresponsible. Most of the overreaching reviews of the game come from people who never played older RPGs and think Undertale is revolutionary in areas where it's actually bland.
I think the only thing Undertale did very well was the soundtrack. Everything else was okay but not great.