Pander might be a bit harsh.

And staff connections as well as Gravity Falls' immense popularity (as well as not shitting the bed) would help out a lot too. Plus Disney loves themselves crossovers/references.

Star Vs. should forever be remembered as a cautionary tale on not planning your plots out and taking the time to consider the implications of your actions. Mass genocide of innocents shouldn't be considered a positive.

Many different things really, Eclipsa even mentions just killing Mina outright to try and steer everyone away. At the very least Eclipsa or Moon sacrificing themselves to save everyone could be a bit redemptive. But even then, that doesn't fix a lot of issues.

People mainly focus on the ending, but overall there's a lot of writing problems with the whole season (as well as a bit in 3) that pile onto each other.

Though, if I had to just fix the ending itself, I'd just do the opposite of what the show does. Instead of erasing magic, just give it to everyone. To parallel how cleaving the wand the first time allowed both Star and Ludo to use magic, it then allows every Mewman and Monster to use it, albeit their magic being considerably weaker than how it used to be. The monsters are allowed to fight back, Mina and the armor are weakened as a result, the MHC stop trying to control magic, and Glossaryck leaves on his own, telling Star that it's now her duty to help train everyone on how to properly use their new abilities.

Ends on a sense of unity between everyone, Star has a new purpose, and she doesn't end up snuffing out billions of lives only to then be rewarded for it.