There's a ton of very simple "minimalist" or "classless" or "markdown" [0] CSS files that you can apply to plain HTML to get modest good looks versus browser default styles these days. No changes to your markup, just use that raw HTML you are already comfortable with and LINK tag in a single CSS file.
[0] From that idea that sometimes you just want to take a Markdown document's boring raw HTML output straight out of the processor without any other templating in between.
This seems like a very good list with lots of handy easy to compare preview screenshots: https://github.com/dbohdan/classless-css
[0] From that idea that sometimes you just want to take a Markdown document's boring raw HTML output straight out of the processor without any other templating in between.