To be fair, I think there's a reason why Nick went with the crossover with the 80s Turtles to be the last episodes they actually showed. With how much they crossed over, it still feels like a decent finale without being as dire as the Future three-parter. I'm not sure the future arc hits the same way as when it aired, since at the time Mad Max Fury Road was a big deal, but now it kind of has to stand on it's own.
I guess it's become tradition at this point for the TMNT to have a dark future. Nearly every series seems to do it.
And, yes, agreed on this being the best crossover we've ever gotten with Usagi Yojimbo. We actually had a little bit of time to explore his world. Arguably, the best official animated version of Usagi we've gottten ever, including the Netflix show.
Personally, I still like the 2003 cartoon the best, but I think 2012 is a close second. It just feels like 2003 had a bigger focus on the plot and some more varied villains. But, I think the 2012 version might have the most fleshed out version of the core characters. And some of those moments of horror were REALLY memorable. When it was going full-on horror movie it was powerful stuff.
And 2012's version of the Mirage Turtles was even kind of memorable. Silent, near-alien feeling Turtles since they're from a completely different medium than the cartoon-based Turtles. Comics have no sound, after all. Kind of clever.
But, I think the 2012 version of Shredder might be the most forgettable of the cartoon Shredders. Some of the stuff that happens TO him is interesting, but he HIMSELF isn't really that interesting. And I think the first two seasons leaned a little too heavily on the Kraang for my liking. But, your mileage may vary.
And, I hope you have fun with Rise, too. Just...keep it mind it's trying to do something completely different.