someone, somewhere, has offered a potential blueprint for how to put goals past that exposed rear that City deployed.
Yes....and no. From my perspective, Man City have never been a really defensively solid side. And I think that comes down to a combination of transfer policy, coaching and the tactical system. Pep is not really interested in defending per se. He doesn't want 'defenders' in his squad. He believes his system will holistically take care of both attack and defense and he doesn't want his team in a position where they are 'defending' in the traditional sense.
Like Klopp, it is the deliberate acceptance of risk in exchange for what Pep believes is a winning formula when you have access to elite players. In other words, at this level, defending as such is a waste of resources, or indicative of a lack of imagination or ambition. If you control the ball and your attack terrifies opponents, you don't really need to defend - your opponents will be doing all the defending. You'll allow counterattacking breakaways from time to time, but with a world-class keeper between the posts you'll save some of those anyway.
The flip side of this is that Man City can be got at - and always have had this 'weakness.' But few sides have the mental and physical discipline and skill to really put pressure on them. When you do, they crack. But can you outscore them?
Note, also, that while Chelsea put four goals past them, they leaked an equal amount. That's only good for a point. A good result for Chelsea, but no manager is happy to get scored on four times.
And, finally, there are a few teams out there (Atelico Madrid under Simeone comes to mind) who are philosophically opposite - and have had success as well. That's one great thing about football, in spite of what pundits may say there isn't a 'right' way to play football.