It's all well and good having a system and sticking to it at all costs if you have effectively two squads with all the players you need, like Pep.
However, the best coaches can adapt to their given situations accordingly. Playing a highline constantly to the halfway line without the fastest defender in the league (who bails us out often enough, maybe too much to the detriment of his own physical wellbeing?) is simply asking for trouble. Saudi Sportswashing Machine aren't even that great. Imagine that was vs Arsenal, Chelsea, Liverpool? They've even more sped than Saudi Sportswashing Machine!
How much did we dislike Conte in the end because he was so inflexible given what he had/didn't have at his disposal?