You are probably right when you say it's become less powerfull than it was before, but it can still rip up decks. But it won't be winning any major tournaments if that's what you meanÂ

What do you mean by that? Should a MUC deck run B2B main or SB when going to a tourney?
Personally, I would still run 2 mainboard. The chance of getting paired agians Staxx/Dragon/other decks that still use mostly nonbasics is pretty big. Then, if you get paired agianst Gifts, you can side them out for Gifts hate. If you get paired against one of the 'nonbasic decks' you can side 1 or 2 more in.
You'll have to tweak the perfect number of maindeck Back to Basics, according to your metagame.