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
You can create clean separation in your code to make this easier to understand but it’s not well enforced by default.
The criticism is that by allowing you to do something you shouldn't, there isn't any benefit to be had, even if that system allows you to do something you couldn't before.