Bunting is a clear downgrade on Guentzel without a doubt, but I also think the top line isn't going to be much worse without Guentzel than it was with Guentzel. Now this really changes if Crosby falls off, but Crosby has never had any issues maintaining an elite top line with or without Guentzel.
I think the roster today is effectively the same as the roster last year. Hayes, Grzelcyk and Beauvillier in and Carter, POJ and Smith out seems mostly like a lateral move. This team isn't done though, since they do have $6 million in cap space left. But all they've done so far this off-season is maintain the team as-is while getting 2 2nds out of it IMO.
I think this reinforces even more that the Leafs don't have money for Robertson.