Your sites are clean and look good. But rather than seeking other things to learn, IMHO you should stay at this level for a while and fine tune the speed and check for vulnerabilities in your code.
Learning new stuff is always fun. But looking back and fine tuning is boring. But from my view the best way to learn. Almost every day I use https://web.dev (and similar sites) in order to be even better.
Disclaimer: This is a personal opinion. jQuery, Tailwind and Bootstrap are shortcuts that may block your attempt to learn web developing from the ground up.