See, the ending didn’t come across as one big nihlistic joke to me. It called back what Morty said to Summer and the Council during their trial: “I don’t renounce Rick, and I never have… I wanted [Summer] to have a normal life; that’s something you can’t have once Rick shows up. Everything real turns fake, everything right is wrong, all you know is that you know nothing and he knows everything, and well, he’s not a villain, Summer, but he shouldn’t be your hero. He’s more like a demon or a super fucked up god.” That batshit crazy Rick that Morty follows emerges in the garage at the end, just like Morty said he would. And even though Rick says all that weird shit, I don’t believe it. I think it’s his response to all of the planet/family shattering stuff that has just happened. It’s easier to just claim it’s all for some McNugget sauce than for Rick to actually say he made choices that hurt his family.