That’s a decision the add-on author has made. You don’t lose the ability to sync with AnkiWeb each time an Anki update comes out.
What are you basing that claim on? I checked the report logs, and the only post by you that was flagged by a user was this one, which is still visible: Create a Anki LTS Version - #11 by krstoevan
Developer resources are constrained as it is, and maintaining multiple versions would make the problem worse. Ubuntu is a large company, and can afford to dedicate people to taking care of such things.
The new editor did make things slower, but it did bring a bunch of new functionality at the same time. The other main cause of slowdowns is web toolkit upgrades. You can use the Qt5 version to avoid those, if you’re comfortable using a web toolkit that no longer gets any security updates.