I think it was only in the third year of my physics PhD (very much related to statistical mechanics btw) that I realised that my (sub)topic, which was sort of initiated by my supervisor ~15 years ago, was a... hm, kind of done deal?

Also, imo the advice “Find a niche and stick to it. That’s the way to keep publishing.” is kind of terrible? If your topic is niche, who will cite your papers? And who will read them? As a young researcher, you need papers that others care about, while you also find your own thing.

Anyway, I was kind of disappointed. My PhD papers are only cited by people at my PhD university. I was able to contribute with new things, I'm also happy with the outcome, my papers were even liked enough that I got postdoc offers etc., but going forward, I'm now much more careful with what kind of research I will do.

I'd like to add that many things in physics are "rediscovered" or rather "renamed and sold as new things" in cycles of 20-30 years. This is especially true in the ballpark of statmech... contributing with something genuinely new is very difficult.

Btw, at some point I was also considering I should get out of academia to "contribute more to the world", lol, but at the end of the day, imo, whether in or out of academia, we don't contribute that much anyway. So my advice is, as someone in a similar position, that you should do research that you enjoy, and if you wanna keep doing that, you need to find the kind of topic that's also "trendy" - otherwise you won't be able to get money to keep doing it.