I struggled with Markdown (and various other mark up formats) for a long time, until I realised that, for me, nothing beats plain HTML for simplicity and expressive power.
I now use HTML the way people generally use markdown: as an open, easy to read, easy to write, plain-text format for taking notes, writing articles, expressing thoughts, and so on.
I didn't really choose HTML, I just sort of noticed that I was using it. It seems like an unconscious decision, like a river flowing downhill, finding its own path.
Most used tag would be <p>, because I write a lot of essays and things with paragraphing. As well as other structural elements such as headings and lists, I lean into <time>, <cite>, <abbr> a lot.
I tend to use the 'optional' form. I don't close <p>'s and <li>'s unless required.