In comic books they go from big bad guy after big bad guy over and over. Keeps going. A Thanos level threat every other month.
But in movie form, Thanos really felt like the end. The biggest threat they could ever have. I don't feel like Kang could reach that level only because Thanos already did it. Even if Kang is the most dangerous person in the multiverse. Your brain kinda goes ( but, well, Thanos was big and strong and he beat up hulk. Thanos literally succeeded in what he wanted)
So it's like your brain kinda goes, " avengers literally died with Thanos, entire universe was affected" Kang could destroy the universe
But you go, " well there are hundreds of universes so the main universe is not unique anymore"
Kang is cool but he still doesn't feel as dangerous? We don't even know what he wants. We don't know why he's bad. They told us, but didnt show us. Yeah they talk about kangs fighting, destroying universes, but it feels so abstract.
Thanos goal was clear. Thanos was ruthless, one minded. Kang is more abstract and confusing.