Playing defensively doesn't mean give every objective to the enemy team
I don't know how else to word this, and I've worded it in several tens of trillions of iterations. If you are an all assassin team, you aren't going to be able to properly defend even yourself, much less anything else. And if you, as an entire team, do nothing but teamfight the jungle camps for ten minutes straight, all you will get out of it are three dead inhibitors.
Playing defensively doesn't mean abandoning every objective to the enemy. It's about PREVENTING them from taking objectives. If your only line of defense is a fucking utility support, then you have already lost.
I don't know why this is so impossible for people to comprehend, no matter how many tens of millions of times they make this exact same mistake.