I am a Sitecore newbie, but I have been doing front-end development for many years. My first impression with Sitecore is that the front-end is quite "ancient". Out of the box components are jQuery based, no ES6... But I still find it very promising and customisable. I am trying to find the best ways to create themes using the latest standards, including code splitting, and following all the best practices to improve performance.
I would really appreciate if anyone could share links, tips, books or anything that would help in my new role.