It's very common today for FE engineers to have a very limited understanding of the basics because they picked up client-side tech by following React tutorials (or any other highly abstracted framework).
It's a very incremental learning process, so expect your brain to take some time to learn to identify small details that make great UI/UX. It takes practice!
Once you feel comfortable building a simple page, explore various techniques to make it feel more professional (i.e. identify why your page doesn't look as good as some other references, and start copying their ideas).