My years of backend before that certainly influences how I see things. Maybe it would have been better if I'd drank the "modern front end" kool aid from day one. I came in a sceptic and remained one.
The front end world is a miserable place of dreadful software built on fantastic foundations.
I have dabbled periodically in modern front end development, but it depresses me hugely. All the mistakes that gave us PHP dominating back ends (another sad story) being repeated in a modern context.
Learn CSS? I did. Feel like I wore out MDN but I agree it is awesome. An adequate solution to a very difficult problem.