Here's a tip, guys. When you're two inhibitors down and you are pushed in...

...don't go out and try to fight the enemy team. Seriously. Unless you can fight them 4v5 and there's a really good wave clear champ on your team to defend. don't. If they're getting Baron, it's practically theirs. Let them have it and defend your god damn base from the super minions. Sure, they'll come back to hit your base, but with smart usage of turrets and peeling you can use home advantage to fend them off, or better yet punish mistakes and win.

I just came from a perfectly winnable game where I was the ADC and defending base. My team just left and started fighting the enemy team, and they were losing handily because, duh, you left without your ADC. Of course, I went and cleaned up their carries and came back, but even that came back to bite us as the minions swarming in took our nexus turrets and Wukong backdoored us.

The moral of the story? Learn to defend and potentially come back from a losing game. The reason it feels like it's hard to come back from losing more than one inhib is because nobody knows how to defend their base. It's technically free farm and XP coming in, use it to catch up!