Pep absolutely encourages his wingers to take people on. The problem is most of the time our wingers has to take people on from a standing start because of the parked defense and this is almost impossible to pull off unless you're someone like Messi or prime Hazard.
Though what Pep wants is for the winger to only dribble when you're one v one. A lot of our overloads on one side of the pitch is done so we could create a 1v1 situation on the other side of the pitch. Dribbling against 2 or 3 players will just result in a possession lost and discouraged by Pep.
Look at what Kinglsey Coman here said about Pep's instruction to him:
The new Manchester City manager developed Bayern Munich youngster's raw ability and he could do the same for England man
www.manchestereveningnews.co.uk
Basically it doesn't matter if you keep failing taking people on 1v1 because you only need to succeed once to make a difference.