i did just that a few minutes ago. closed my account and removed my one Plugin from the repo. if the statistics in wordpress.org are correct it was used by ~20k sites (though that number is hard to believe and seemed way too large for the usw case for a long time). It can still be found in github but will no longer get any updates since I haven’t used wordpress myself for quite some time and with the current shitstorm i don’t see a reason to invest any time in it.
Having a custom domain for email also makes it a lot easier to move email provider in the future if you want/need to since your addresses can stay the same as long as the new provider supports catch-all for all the aliases.