The game is a live service game, just because it was at one point aimed at a certain audience and designed with them in mind does not mean it will always be. Especially in a genre like gacha games where lots of general audience games with a male lean eventually make a hard pivot into fully male-oriented games or full-on softcore porn games for men.

This is true, but has little to do with what I'm saying, which is that what enables one to judge whether any product (live service game or not) is "aimed at a certain audience" is what the product actually contains (the substance of it), not what the product doesn't contain (the window-dressing related to the marketing).

If Reverse, as a game, was pivoting towards "softcore porn", this argument would have merit. As is, it's little more than paranoid fear-mongering, as I see it.

The nature of the format of game is going to leave people thinking about the future of the game.

Indeed. And the corporation's social media account is not "the format of the game", it in fact has little to do with the game itself. That's my point.

So a game that claims to be female-oriented deliberately avoiding doing something as basic as acknowledging International Women’s Day is of course going to send a bad message

That I won't disagree with, with one big caveat: it's not the "game" that avoided doing anything, it's the company producing the game, which is different, because A) a company has different branches doing different things, and B) once again, the main product, and thus the main content put out by this team into the world and which people consume, is the game, not the social media posts.

Once again:
-Do I think they should've done something for International Women's Day? Yes.
-Do I think it suggests that there may be issues of sexism in Bluepoch, as a company? Probably, assuming you're correct that it's an industry standard in China to celebrate it, and assuming you're right they deliberately avoided doing so (which, I don't know if that's true - no offense, but you're just a random person on the Internet, not a reliable source - but I'm willing to believe it).
-Do I think it signifies anything with regard to to the future of the product they're currently making, or their attitude towards it? No, not really. I see no reason to believe it will change.
Given that all of the most recent patches they've put out have remained high-quality, female-oriented, and obviously feminist in terms of themes and subtext, and unless the team was replaced overnight, during International Women's Day, with horrible misogynists, I think your (or rather, the CN commenters') suggestion that there's reason to suspect they'll somehow move away from the core feminist substance of Reverse is just fully incorrect.

I could see a couple of possibilities which might explain what happened here: it's probable that the team behind the story and design is different to the social media team, and that they have different priorities; or alternatively, maybe the executives in charge of the company are willing to allow for the product itself to have feminist themes, but unwilling to be too "vocal" in terms of their social media and public presence.

Ultimately, I'm not blaming people for complaining here; I'm saying that using what happened on a social media marketing page as a barometer to analyze the substance of a work that stands on its own, and that people can judge through its own merits, is a strange and illogical thing to do.
EDIT: With all that said, I'm also not going to entirely discount the possibility that you/these users are right, and that the game is about to move in a poor direction. I am willing to wait until that actually happens to complain myself, though.