lit-html isn't _just_ about using standard JavaScript syntax. It's also about being more efficient than VDOM, very small, and having great HTML integration (you can set any property, attribute, or listen to any event, unlike with React).
Yes, you need a plugin for type checking with TypeScript. That doesn't seem to be a huge problem for users so far.
I appreciate that it's more efficient than VDOM, if it's true and continue to be true in larger scale apps. I don't see "can set any property, attribute, or listen to any event" a benefit though. To me it's such an unpleasant way of writing code to have to keep in your brain a map of all these event and prop bindings.
If you need events, Rx is much better to work with. Probably the one thing react is not as good as html elements is the lack of attributes, this causes a lot of defaultValue and shouldComponentUpdate kind of complications. However, if you really think about it all props should just be immutable (attributes) and if you want some to be updated or emit events, just make them Observable and Observer accordingly.
Yes, you need a plugin for type checking with TypeScript. That doesn't seem to be a huge problem for users so far.