In reply to Peter Shaw.

The challenge is a lot of legacy code within plugins/themes that rely on jQuery. For example - in my company, much of our animations still run on jQuery itself. There's nothing wrong with it, and it's a quick fix to simply call the jQuery library within the theme.

But all the small business WP users who are managing their pizza site off a 2017 WP theme that uses jQuery can't get that dev support at all. And that's the internal struggle the WP core team is having.

Now that I think about it - maybe it is something like a basic plugin that calls the jQuery library, so WP Core can migrate out to vanilla JS -- while the plugin is what supports the legacy owners.