I'm a developer who strongly believes in solidifying and building on fundamentals before jumping onto hyped frameworks, languages, etc. The basic constructs of any technology, language, framework, etc. are the same. It's only the abstractions that change. I'm more interested in the "why" rather than the "how".
On the coding side of things, it's quality over speed for me. While it may seem that you are saving time in the short-term by churning out low-quality unmaintainable code, you are actually just pushing that time to the future in the form of slow patches, technical debt, etc.
Hence, clean and maintainable code is something that goes a long way in building great software. P.S I'm a big fanboy of the book "Clean Code - Robert Cecil Martin". If you ever meet me, chances are you'll hear me talk about it as if the publishers pay me to do so LOL.
I have worked on the full stack in web-dev but am more focused on backend technologies. Gotta be a T-shaped developer nowadays.