@epistemophagy I agree with some of your points here, and I share your frustration to a considerable extent, but I am also not quite as worried about this scenario:
1. Twitter isn't viable anymore and it will be more apparent over time. Advertisers are not staying, the alternative money-raising mechanisms aren't working out, the regulators from the US and EU are circling, Musk continues to fire people without regard to what they do, and the number of tech issues at the site seems to be on the rise even as Musk guts staff and turns servers off. Journalists may not have (all) left yet, but it's only a matter of time before they have nothing to remain on there.
2. Most of the issues with onboarding are due to a lack of clarity in explanation and presentation (Join Mastodon is pretty narrow in the list of sites it features) more than actual difficulty, as well as certain prominent Twitter users being dismissive of attempts to leave. Some smaller, older instances can be very petty as well (don't get me started on the crap I have seen) which has affected one person I know who got banned from a smallee server; this has been an issue on Fedi since well before the current wave, and I suspect it is due to it being previously a refuge for people who didn't fit on mainstream social media for whatever reason. My suspicion is that this will change over time as different new parts of the Fediverse, Mastodon or otherwise, grow.
And I do suspect they will grow, based on several developments I have heard announced ...but more on that later. I think I need to get back to celebrating with my family. I will follow up on this later tonight.
Merry Christmas, Happy Holidays, or whatever you prefer: be safe and happy during this last week of the year.