I have now firsthand seen the context for the "Kendra is a lesbian" and "black lady replacement for Johnston" in the remake.
In Kendra's case, it is literally the most throwaway of lines given in response to the fact that Isaac has been rewatching a video recording of Nicole nonstop and it doesn't
necessarily insinuate that Kendra is gay – that's just one POSSIBLE interpretation that could be gleaned from what she says:
That's it. That's the line. And that's all that's ever really said about it. It's not exactly shoved down your throat, moreso it's thrown out there into the ether.
In black woman Johnston's case, she doesn't join the the initial boarding of the Ishimura because she apparently injures her ankle during the Kellion's rocky entry into the Ishimura, so while that makes it to where she doesn't IMMEDIATELY die alongside Chen in the opening beats, she's still doesn't survive past Chapter 1 (not to mention the fact that she has a total nonpresence from when you leave her on the ship to when you come back to it) as, when Isaac returns and the Necromorphs destroy the Kellion's singularity core, she ends up dying to an explosion and her body's lost with the Kellion going down in flames. Though she lives longer, she remains a nothing character and goes out essentially like a nothing character anyway.
(I had another screencap to spoiler and post for the Johnston death scene, but the Farms is currently being a stubborn bitch about uploading a larger image like that. You can look up any video on it for yourself to see that she's not exactly given a very dignified or glorified death. She stops to blast on a Necromorph popping out of a side room in the ship, and as soon as you walk up — Boom, dead, and Isaac, through plot armor, is blown out of the ship to safety.)
These are two more of the things that have caused continual kvetching about how awful this remake is. Positively ruined by [current year] political bias, I tell you. Absolutely game-ruining.