OK, there's quite a lot to unpack there. Three main points I'd say.
Dealing with them in reverse order.
"All of Hollywood has been genderist until recently" doesn't mean actually doing anything meaningful to promote trans inclusion. It means parroting a party line. It means saying, "Of course trans women are women" even when, as a heterosexual man, you know full well you would never date one. It means all jumping on that bandwagon to denounce JK Rowling and her awful transphobic views because believing in gender ideology is fashionable and insisting on the reality of biological sex is not. I don't think half the people parroting these things genuinely believe them, but it certainly has been and still is the only acceptable viewpoint in Hollywood. I think this is particularly the case for women in Hollywood, most of whom are either so young that they're just starting out and desperately need to get breakthrough roles, or ever so slightly older and therefore need to still be considered young and fashionable and relevant otherwise they'll age out of the business even quicker than most female actresses already do. One ill-advised comment about how JK Rowling might have a point can easily see you consigned to the "has-been" heap and never get another role.
In terms of trans people being represented in films, I mean, yes, there are a few, but the reality is that there aren't that many trans people in real life as a percentage of the population and so most stories are not about them. You can't put a trans character in something like Shakespeare or Jane Austen without making a decision that you're going to "queer" the whole production, which many audiences will find off-putting. It's difficult to cast a trans person in a regular movie role involving a romantic storyline or a sex scene, because most viewers aren't going to relate to that, and people like to watch things they find relatable. There's also the issue of how you portray the relationship. If it's between a man and a trans woman, are you portraying it as a heterosexual relationship or a gay relationship? Because either way you risk offending someone. You could write a trans character into something like Emily in Paris, for example, in the role of "eccentric friend/sidekick". But ultimately it's going to be quite difficult to give a trans character proper character development (and avoid tokenism) unless they are the main character. It's much easier if you're making a series and the trans character can be one of many characters who get plenty of development over several seasons of the show. But in Hollywood, in a two hour feature film? Not so much. Either you're making a film about a trans person, or you might have opportunities for token trans people at best. This obviously has a big impact for trans actors, because trans actors are generally limited to playing trans characters. Elliot Page has only ever played trans characters since transitioning. A trans woman actor can't convincingly play a female character, and probably wouldn't want to play a male character. So opportunities are obviously going to be limited.
As for the dating trans people issue... Well, that's possibly the most awkward one.
I think Hollywood has reached the point where more, hopefully even most gay and lesbian actors feel comfortable being open about their sexuality and being seen with a same sex partner on the red carpet. (That said, we have no way of knowing how many actors are gay but not out.)
Dating a trans partner is on another level though. The uncomfortable truth is that most people do not want to date a trans person. Most of us are sexually attracted to people of one sex only, and we like the external presentation to match what is underneath. I would describe myself as a 95% straight woman (I have had experiences with other women but I am only really interested in men), and yet I would consider dating a woman but not a trans woman. Even though a trans woman may have all the same body parts as a man, and I am attracted to men, and even though I do actually believe that trans women are men, I am not attracted to men who present as though they are women. Nancy Kelley, the former CEO of Stonewall, who likened lesbians who would not consider dating a trans woman to "sexual racists", is not known to have ever dated a trans woman herself. Neither is Layla "I'm pansexual" Moran. They're all a bit "TRA in the streets, TERF in the sheets".
I think that if you are not trans and you date someone who is trans, it raises all kinds of uncomfortable questions about your sexuality. If you're a straight man and you date a trans woman, does that mean you're actually gay or bisexual but in denial? (In my opinion, yes.) If you're a gay man and you date a trans woman, does that mean you don't believe they are really a woman? (In my opinion, also yes.) If you're a lesbian and your wife, let's call her Ellen Page, transitions to become a man named Elliott Page, are you now in a heterosexual relationship? (In my opinion, no. You are still a couple of lesbians, albeit one of you is very confused.)
Do you not think it would be far more scary to step out onto the red carpet with a trans partner, knowing that the internet will be buzzing with people speculating about the quite literal ins and outs of your sexuality, when you may not really understand or accept it yourself? Much more invasive than press coverage of, say, Portia di Rossi and her wife both looking beautiful, or Neil Patrick Harris holding hands with his husband.
I can quite understand why nobody is walking down the red carpet with their trans love interest, and no amount of measures designed to promote the inclusion and acceptance of trans people are going to make much difference to that.