Speaking as a front end developer with 4 years experience using Lit -

It’s like using jQuery in the mid 2000s - it’s not like it allows you to do anything you couldn’t normally with vanilla JavaScript, it just provides some shortcuts for common scenarios. The process of defining the class that controls a custom html element is a bit of a slog in vanilla JS - in Lit, especially with Typescript decorators in play, it’s a breeze. It saves time and helps keep things fairly DRY.

I should think the dream is that Lit, like jQuery, will slowly get absorbed into the web components spec itself, until all the things you used to need to reach for a library to do efficiently - will simply be a part of the vanilla language itself. Like jQuery’s css selector functionality has now been superseded by JS’s querySelector.