Not true.
It's not a coincidence that characters of color are either totally not included or outright disregarded when it comes to shipping.
Most of the arguments about Bucky's place in Steve's life can be made about Sam (but almost never are), and there are plenty of canon examples to justify Iron Husbands being one of the biggest slash ships in the MCU fandom, yet half that ship is studiously ignored to favor pairing its other half with any other cis white male characters in fandom, etc.