On that point i note that you can, if you have a paid account use Fedica to post on Mastodon within Hootsuite - but surely they are considering navite supoort? https://fedica.com/blog/how-to-schedule-mastodon-posts-in-hootsuite/
I find it really weird that https://www.gov.uk/guidance/social-media-playbook GovUk’s own playbook has no references to consideration of open government, freedom of information, or universality of access when it comes to social media.
I think your points are valid. There is still work to do to enable government amd corporate agencies to easily operate their own domain in fediverse. There are projects and server hosting providers that are making that easier but realistically we need to see those services become much more integrated with existing social media, website and email management tools ( Think software like Hootesuite, SproutSocial, HubSpot on the client side and GoDaddy, AWS, Azure, 1&1Ionos on the server side ) that include managed activitypub services to SMEs and corporates and a way of managing them. I see these being like email accounts, only available for use by the domain user but can exchange content through federation. Moderation in these cases is just like dealing with Spam (Which email providers already do) - I know these approaches mean that at the infrastructure level there is a tendency back to centralisation but the difference is that there is no lockin. A company/org/Person can take their website / domain to whatever infrastructure they want.
On that point i note that you can, if you have a paid account use Fedica to post on Mastodon within Hootsuite - but surely they are considering native supoort? https://fedica.com/blog/how-to-schedule-mastodon-posts-in-hootsuite/