I'm not saying that this is the hurdle you're facing, just to be clear, but...I consistently see people doing things that are either ineffective or straight-up counterproductive to getting RP.
Vaguely saying in a lounge, and sometimes even saying on faction channels,
Player is trying to decide if they want to RP tonight!
or,
Player feels like RP!
--I almost never respond to this, for a whole boatload of reasons. I'm not an elitist, and I don't just like to RP in a corner with my friends, though that's often how things go, because my friends actually specifically ask me if I want to RP, and usually they have an idea as to what we might do. So many of the people I see complaining about cliques and being left out of plots never actually page a scene-runner and say, 'Hey, your plot looks awesome! Is there a hook that would allow me to get involved, or somebody I should talk to about doing that?' Most of the people I see in lounges who announce they are debating RP tonight never actually go so far as to ask anyone specifically for a scene, or put in the thirty seconds of time to check someone else's character info and suggest a scene that might appeal to them, or check the +events board and ask people running plots if their character could follow up on something that happened, or propose something they could get going on the grid, no matter how simple -- or any number of other proactive choices.
Which almost inevitably seems to lead to this kind of player disconnecting after making some kinda passive aggressive remark like, 'Player guesses they'll just give up for the night, then.' And while I totally understand that it can be frustrating not to get traction on a game, this behavior is not endearing. That person becomes someone I sorta plan to avoid.
Which kinda leads into the other thing I think people don't keep in mind: many people still doing this are grown adults, many with children and full-time jobs. Some of us enjoy ST/GMing, particularly large-scale, long arc plots. There have been times mid-plot when my free time for RP is booked up for literally two weeks with people who need scenes with me, in addition to whatever funsies I'm doing for myself. It gets difficult to do spontaneous RP for scheduling reasons, and certainly there's only so much creative energy anybody can put into this stuff without going insane and burning out. Sometimes, it's very much a kindness to very specifically ask someone for a scene, suggest something you think might be fun, and then plan a day to do that. I sort of miss games where the culture leaned into 'random grid RP,' too, so I get where you're coming from there...but, that's just the way things have trended, so all you can really do is try to be more direct.
People do not page, though. I sure can attest to that. I've run enormous plots on numerous games, and more often than not I wind up hearing about salty players who say they can't get involved, who have never once actually paged me to ask me how they can do that. I'm a very not-scary person to interact with.
Honestly, I think most people are flattered if they're approached for RP by a polite person who has an idea as to what the scene might be.