Grealish and Mahrez with inverted/CB fullbacks was a terrible idea and always is a terrible idea. It's much much easier to defend. Aside from the added energy that Bernardo, Foden and Alvarez brought, Foden/Bernardo on the left and KDB on the right made Dortmund spread and left space in the half-space.
Pep's a genius but I don't understand what he expected from that first half set up, as it doesn't get the best from any of his players. I don't think any of them played that badly, but they were ineffective.
Ah well. John Stones is epic and Haaland is an absolute freak - no one else scores that