It's not that hard to understand so don't bring Halo into this mess.
In the article it's also stated that piano only ballads were a thing since long ago but somehow none of them reached top spot before Adele. Your reaching five years like those things weren't done decades ago
SLY was only accompanied by piano, a solo piano w/ vocal song. (Though it did use background vocals/vocal doubling.) Unfaithful and TAB are not vocal-and-piano songs, no matter how you cut it. Please stop.
I don't see the issue here. Adele did lead the way for a more downtempo/acoustic/instrumentral/alternative dominance on mainstream radio after dance-pop dominated for a couple of years. Not necessarily saying that they need to give her thanks, but Adele played a major part in that swift change in the pop climate. Give credit where it's due.
