I would argue that developers who aren't having fun are going to create bad products. They certainly are not going to push themselves or be particularly creative. I further don't believe for a second that the utility of libraries like moment.js (and the many improved children it inspired) has anything to do with maximizing "fun". Depending on your objective and perspective, they make the job tolerable and/or possible with far fewer bugs than would exist if you tried to build something from scratch.
I do have good news for everyone, however: you can use tools like Stimlus Reflex (Rails) or LiveView (Phoenix) to build reactive UIs that require none of the heavy client libraries slowing down your pages. Using these tools is simpler, faster and indeed more fun because you're managing state changes on the server and only delivering the bytes that have changed.
Here's a reactive tabular data navigator that supports sorting, filtering and paging without any app-specific JS code required, period. Total JS payload is 54k over the wire, and to be clear... that's for every example on the site.