The technique I used here and in all my browser-side code is the exact same technique used by VS Code internally, and it scales very well. The only difference in my code is it's more concise than writing 10 lines to construct and setup a DOM element the typical way.

Honestly, the real interesting part about my framework is literally everything else. Returning strings from JSX on the ssg-side; being able to import raw source directories and manipulate string|Buffer at ssg-time; the extremely efficient and lightning fast module system I wrote on top of chokidar and swc; probably more I'm forgetting, but basically the JSX-as-DOM is only the most visually interesting part. But really just a party trick.

[edit] Case in point: the source code to vanillajsx.com is extremely concise and clear and short, I literally wrote the whole thing today with zero deps (besides imlib), and the JSX-as-DOM demos are the least innovative part of it: https://github.com/sdegutis/vanillajsx.com/tree/main/site