Considering Supergirl’s declining ratings, there are others who point out that its real problem lies in being Superman in drag or something in the lines of that. Mike Smith’s classic anti-Supergirl essay predicts many of the problems that would plague the programme.
In here Kara Zor-El’s backstory is linked to Superman but very convoluted. She’s forced to become Supergirl by her peers and gets mentored in a way Superman wasn’t subjected to much.
Also her stories are just Superman’s with different characters in it. You could swap National City and its cast for that of Smallville and nobody would care or notice.
The inclusion of Kon-El would make things worse. First off he’s going to turn out to be James Olsen’s little brother, giving him another super-being for him to overprotect and latch onto.
He’d also make Supergirl redundant. That’s the greatest foe Supergirl has yet to defeat. There’s another solar-powered alien superheroine named Starfire and she outSupergirls Supergirl.
Then there’s Miss Martian who’s a teenaged female counterpart to another alien hero, Martian Manhunter. Then there’s Shazam and Mary Marvel. With these characters around, there’s a good argument to why Supergirl should become her own person.
But if Kon appears, he’ll only worsen the actual programme and might end it for good.