With the vlemmy situation ongoing, i feel like it would be useful to put this here (i did not make either of these tools)
Lemmy Account Settings Instance Migrator (LASIM) copies all your subscribed communities and blocks and lets you upload them to another account, in just a few clicks
lemmy-migrate does the same thing but without a GUI and support for uploading your backup to multiple accounts at once
it went offline and no one really knows what’s going on
I think it may be too late to follow your advice
For vlemmy it may be too late, the point is you can use this tool going forward at your next instance.