They lend you optionality of when and where you want your code to run. Plus it enables you to define the server/client network boundary where you see fit and cross that boundary seamlessly.

It's totally fine to say you don't understand why they have benefits, but it really irks me when people exclaim they have no value or exist just for complexity's sake. There's no system for web development that provides the developer with more grounded flexibility than RSCs. I wrote a blog post about this[0].

To answer your question, htmx solves this by leaning on the server immensely. It doesn't provide a complete client-side framework when you need it. RSCs allow both the server and the client to co-exist, simply composing between the two while maintaining the full power of each.

[0] https://saewitz.com/server-components-give-you-optionality