About the only mark against the series is that we didn't get an Adam mention. But, given the relationship stuff that needed to happen in the final season, that is okay.
I liked that the season went more into the dichotomy of science and magic. And a lot of the lore implications has me eager for a sequel series.
Horde Prime was just perfect as a villain. Still shocked that they didn't use Hordak as their Horde guide, but Wrong Hordak was just wonderful. Adding another fun character in a cast chock full of them is tough, but they pulled it off. Plus, Hordak telling off Prime was great, if sadly a bit futile. And though the cast that remained on Etheria did not get a ton of focus through out the series, it was enough for the gut punch when Prime took them over. And even though we did not get a lot of the classic Horde villains, the Horde we got was more than sufficient.
And man, if you had seen how gay the last seasons were, it had nothing compared to this season. Went crazy with the gay. And they definitely had put the work in in order to make Catra and Adora work after everything. The kiss is clearly a bit deal, but I am just as impressed with how blatant they started to make the flirting. Of course, they kind of had to make everything a bit over the top, to beat it into the stupid idiots who will whine about the pairing.
And I will say, I enjoy them tackling the issue of "the chosen one" and not sacrificing your self for others, just because you are told to do so. This is something that is generally covered in a sequel series (kind of covered it with Aang in Korra) or the coda season (Stephen Universe).
And I love that Stevenson continued to make the First Ones dicks. And their containment of magic is kind of interesting. But the First Ones Rebels, operating out of Grayskull Base has a lot of fun lore implications for Eternia. God, do I want a sequel series of the Quad (with Entrapta, of course) roaming the universe.
Also, Entraptra/Hordak is weak (though I loved Mermista's WTF reaction), Entraptra/Darla is the true ship