The Carol Danvers version of Captain Marvel is straight in the comics, but there is a lesbian Captain Marvel. She is Phylla-Vell, the daughter of the original Captain Marvel and a member of the Guardians of the Galaxy. In Phylla, Marvel has a ready-made LGBTQ+ heroine who can and should be added to the MCU.
Steve's extreme behavior regarding Bucky in both TWS and CW was enough to persuade me that their relationship could be interpreted as romantic. But it was statements made by the Russos and Markus & McFeely that really pushed that possibility hard. All four of them stated in various interviews that Steve's love for Bucky was the driving force behind his actions in CW. When discussing the helicopter scene, Joe Russo said that Steve had a "very passionate" motivation to put on that display of strength. That caused many fans to assume that
Sharon was in the copter. Steve showed as much
passion for Bucky as he did for Peggy, and far more than for Sharon despite the chaste kiss they shared.
All of this is to say that fans who think it plausible that Steve and Bucky are/could become lovers aren't just creating that out of nothing. Viewing the two of them as bi isn't even remotely ridiculous. The subtext is there and could easily become text if Marvel allowed it to.
(BTW, Steve & Peggy are my favorite couple. just ahead of Tony & Pepper. I don't even like Bucky and I can see it.

)
There was actually a "Give Captain America a Boyfriend" campaign a couple of years ago. It arose from the "Give Elsa a Girlfriend" drive among
Frozen fans. There was even a Twitter hashtag. The backlash was predictably ferocious.