The similarity between Samurai Jack and Star vs. is that both Gendy and Daron are weebs. Samurai Jack was based on Gendy's fantasy of fighting zombies and monsters in an apocalyptic wasteland Mad Max style using a katana while riding a motorcycle with his hot bitchin' girlfriend. Star vs. was based on the overflowing 90s and early null's magical girl shows. Also, both of them self-insert as their respective show's protagonist.
The difference between Samurai Jack and Star vs. is that Gendy views Jack as not being capable of doing anything wrong, so when an instance of him suffering does come up, we don't feel any sympathy for him because he's become a messianic character, since endy gave him all of the "cool" qualities a pleb shounen protagonist would have. We are bored with his references and find his parodies hackneyed. Samurai Jack only made me feel, and I mean REALLY feel, in one instance, and that was the Viking warrior being chosen by the valkyries to get to Valhalla. Sure, the show has excellent choreography, great art style experimentation, and strong sound direction, but it has no story. It tried to force a narrative that the show never had in the first place, and it failed.
Meanwhile, Daron gave Star not just hyper manic pixie "lolsorandumxD" aspects, but gave her all of the faults, fears, and flaws that she, and the majority of girls like her, had when they were teenagers. We can form an emotional attachment to Star because she has real qualities about her that pretty much everyone can associate with, and not just Star, but the whole cast of characters brought along on this wild ride. I actually hurt when they had Freeze Day and Marco saw how all the years had gone by without him talking to Jackie, because I made that same mistake.
That's why I trust Daron with what she's doing. Both she and Gendy created shows based on fanfiction, but at least she had the decency to continually filter out all the unnecessary, unappealing garbage.