Yes, and you'll see that I actually read and responded to your post in that forum. You included some of my quotes as "crapping" on Supergirl, and I took issue with that because it wasn't that simple as you were making it.
If Diana was shelved for the foreseeable after a half assed "trilogy" that she had to share with a ton of guest stars, and Donna was given all her stuff and pre-dated her in-universe, I am very doubtful whatever fondness the WW fandom has for Donna would prevent them from being annoyed at the situation, if not the character herself. Do Wonder Woman fans in general like Donna more than Superman fans like Kara? Donna spends most of her time in the Titans franchise and her ties to WW are tenuous at best most of the time, how many WW fans actually consider her to be essential?
The fans who have a slight aversion to her fighting public domain villains may not be as numerous as you think. And since Wonder Woman has even fewer big name villains who can carry a film than Superman does, giving one of her arch enemies to the spin off character with no immediate plans for Diana herself to confront said nemesis would not go over well at all. There is already some backlash to changing the story to be set during WWI and the demigod origin in place after all, and those are relatively minor compared to a sidekick being the predecessor.
Wonder Woman pre-dating him in-universe as she does now is a non issue. Ditto Batman. Because they are independent characters that have nothing to do with his mythos. Kara is a spin off character and always has been. She didn't exist until two decades after Clark, and the logo is slapped onto her to carry her to success and expand the franchise.
DCEU Batman wasn't any more readily embraced than DCEU Superman, and Batman has had more cinematic outings than Superman. More cartoons and video games too. Do you think WB is seriously thinking of shelving Bruce and having Batgirl set in the 70s and Barbara donning the cowl before the Waynes are murdered?