How the fuck can you call their music dull?
Despite being hugely popular, this is dull:
And this:
And this:
Not this:
Or this:
Lol good trolling, but those songs were based on song writing. Learn some fucking music theory before you try having an opinion you dumb girl.
Def Leopard, is a band based on superficialness. That is why your never gonna hear a reputable band covering def leopard, and why all those other bands you have mentioned have been covered countless times since they were first written.
They sold alot of albums because they had insane production values, and look good on stage. They are basically a boy band.