[bird_monster]

It kinda depends on your goals I think. The T shaped developer skillset is extremely, extremely valuable and will only probably continue. Sure, you could get deeper in a language you already have experience with, but do you think that will better prepare you for future experiences in different languages? Do you want to stick with the tech you're currently using for the rest of your career? If you do, that's great! Don't even worry about the other stuff. But I can say, any time I've spent in my career learning something new has never been wasted time, even if I never used the tool again.

Sometimes it's also fun to just see something different. There is value in "Play". You might find you actually really love the new thing, or you might find the new thing just totally reaffirmed your love for your current tools. Either is great! But finding out is probably more valuable.

For what it's worth, to your question directly, I found using Prolog to be a pretty profound experience with respect to how I thought about programming. I haven't touched it in ~12 years, but while I was using it I thought it was incredible. One of the "funnest" learning experiences of my career was building sudoku solvers in Prolog.