If you like React but also don't want a build step, take a look at Preact (only 3kb gzipped) + HTM, their alternative to JSX that uses tagged template literals, so it works in the browser (but also can be compiled away in a build step)
Lit also requires no build step and is shipped only as standard JS modules. It also uses file extensions in all imports so that the required import map to access all files is very short (one index map + one prefix map * 4 core packages). See https://lit.dev
Lit is definitely on my radar, I'm just trying to figure out a project I want to use it on. I want to update my personal website but Lit's SSR is "experimental" so I'll probably wait and try SvelteKit or something else.
https://preactjs.com/guide/v10/getting-started#alternatives-...
https://github.com/developit/htm