This has been suggested many times, but if you don’t want to read the 4000 words version that Moldbug has, here’s a 255 words TL;DR.
What you want is a manager app:
Why do you want this? Because content creators — which we may define as those 1% of users that drive traffic — don’t want to post manually across platforms, so they use a manager app of sorts to post across apps.
Such apps exist already. The most popular ones are HootSuite and Buffer, but there’s a ton of others. Common for these is that they use the APIs of the existing Big Tech services. That also means they are in line with Big Tech censorship, since if they weren’t, Big Tech simply removes their API access and their product is dead. I submit any competitor that starts here but allows for cross-posting to actual free speech alternatives such as the sites listed above, would get a request from Big Tech to remove their support for such platforms, and failing that, lose their own API access to Big Tech platforms. This situation this keeps the free speech competitors at arm’s length. So the content creators can’t expand to these new platforms and build up a userbase there since they would have to engage in cumbersome manual cross-posting.
The solution here, it seems to me, is to create rogue manager apps that use Selenium masked as a regular user to cross-post content without using the APIs. I don’t know of any such services, but I see no way to stop them realistically, for the same reason one cannot stop spam: AIs pretending to be human is indistinguishable from real humans.