I have my own favourites......Adele is pretty good but I would not rate her as one of the all time greats. I have been singing myself and listening to other singers for most of my 57 years on this planet so I will not say someone is great unless they truly are. She has her flaws....and that song is a bit of a dirge.
Most of you will know that I am pretty discerning and hard to please. So it should be with all of us. There are tons of talent out there so I set a high bar....maybe some who post here set it far too low.