Thanks for all the neat tools!

I find Mithril simple enough to be low maintenance for Single Page Applications. We still use a version one of it on a project launched about ten years ago -- although I use version two for later things. And you can use it from plain JavaScript with no compile step. https://mithril.js.org

I also find Tachyons or similar Atomic CSS libraries to also simplify CSS issues in a more maintainable way -- also with no compile step. From 2017: https://css-tricks.com/growing-popularity-atomic-css/