I didn’t like the Stanley parable. Undertake had bullet hell gameplay. That seems hugely different? I found it’s aesthetic to be kind of annoying personally.
I'm not a big Undertale fan myself (and certainly not a big Toby Fox fan), but I think the bullet hell gameplay was anything but a gimmeck. Traditional RPG combat simply wouldn't work in Undertale, it would be immensely more boring had there been such a low skill ceiling for a pacifist playthrough. Not sure what traditional RPGs you're playing, but Undertale is anything but boring. Unfunny? Sure, it heavily depends on your sense of humor. Kitschy? Indeed, it inherits that from it's roots in Homestuck. But calling it boring doesn't quite line up, in my head at least.