I know that this might be a huge sell, that I'm trying to convince you of something that will undoubtedly happen that at this point in the show is likely never going to happen, but trust me when I say that Starco is not over.
In the recent season four half-hour episode "Curse of the Blood Moon," Star and Marco find out that they have been cursed when they danced under the Blood Moon's light (back in season one) which supposedly caused them to have obsessive-like feelings for each other and with Tom's help, go to break the curse via the Severing Stone. However, in order to do that, they have to sacrifice the memory of the moment when their souls were bound, synonymous with "the moment when they fell in love."
When they both agree to go through with it, they are brought back to the memory of the Blood Moon Ball and dance under the light once more only to find out that maybe it wasn't the curse put on them by the Blood Moon that caused them to have these feelings, as Star states, "What if it was never the Blood Moon?" By then, the severing process is complete, and they only have the memory of their recent dance and nothing more and admit that they see each other as friends.
A lot of fans were left heartbroken after this episode, and I will admit myself that part of me feels the same way every time I watch the scene of their dance, but that heartbreak in my heart is overshadowed with the hope that Starco will in fact return and will be in full force. There is just too much riding on Starco throughout this whole show for it to never be canon by the time the show ends (next month)!
Again, much like the aftermath of "Booth Buddies" back in season three (just a tad over a year ago), a single shipping-related episode that screams at fans to not be taken at face-value is causing fans to quit the show because of the constant teasing but eventual lack of the ship being supposedly shoved in their faces. This isn't the first time I made an article like this, trying to convince fans to watch the show, but hopefully, it'll be the last because sadly, it will have to be.
See also: "For Those Fed Up With Star Vs. The Forces Of Evil And Leaving The Fandom Because Of Shipping Drama, Get Over Yourselves"
I could build a large argument as to why the severing would be incomplete, or if one or both of them lied about no longer having these feelings, but simply, it all comes down to this: look at the events of "Curse of the Blood Moon" as weight off of the two main characters' shoulders. Rather than have them eventually pursue a romantic relationship on the grounds of feelings forced by the Blood Moon, have this decision to get together develop naturally and be by their own choice!
Don't give up on "Star vs." because of what came of "Curse of the Blood Moon," because Starco will prove to be more alive than ever! Only time will tell...