“Every time” is certainly an exaggeration. Just off the top of my head in a minute:

• The Dragon Prince - nobody gave a damn.
• Star Wars [pick any of several releases] - we’ve had various people of color, both human and alien, as protagonists. I don’t remember much of a fuss over that in particular.
• Various MCU things - Brave New World just came out, again featuring Mackie as Wilson - taking the place of the stereotypically WASP Steve Rogers, no less.
• Hazbin Hotel: Vaggie is heavily coded as latina.
• Mobile Suit Gundam: Witch From Mercury - okay, not a non-white lead, but the first Gundam series with a female lead, and a lesbian romance front and center. Once again, no attack.

If I looked around further, I’m sure I could find more. All of these have variously been critiqued for writing, characterization, or pacing, but failed to draw attacks based on the ethnicity (or orientation) of their protagonists.

Is this kind of attack a thing that happens? Absolutely. Is it “every time”? No. I’d suggest it’s more often when a series goes out of its way to bludgeon the audience with a message related to it, or tries to sell a newcomer as a superior replacement for a legacy character, that people can get riled up.