The not played much isn't true at all.
He's started 5 of their 6 CL matches, and they rotate 6 guys for 4 spots in midfield and he's one of them. (Kulusevski isn't, and neither are Ramsey or Arthur)
I don't want to claim intimate knowledge of the player, but I've watched the odd Juve game to see McKennie and Betancur's always caught my eye. The two make a good duo with McKennie barreling all over the pitch and Betancur the more disciplined, technical player who can pick a pass and get them going.
He's a rich man's version of the player people once though Harry Winks could be.