[kettleballroll]

Just as a counterpoint: this very much depends. I probably spent at least a year (probably more) of my PhD (in Europe) just teaching a class I built up from the ground up myself. I barely got any research done the first year I gave that class, and every subsequent year it still took a large chunk of my time. It's part of the reason I spent a total of 7 years doing a PhD (which is long, considering I already had an MSc), during 5 of which I taught my class, and grew it from 10 students in the first year to 200 in my last. But I don't consider that time wasted. I had a blast and found that teaching helped me understand the fundamentals of my fields at an extremely deep level that I'd never reached otherwise. It didn't improve my research output, but I feel that the soft skills and understanding of fundamentals was a real advantage. My future career also didn't suffer, I'm now working as researcher at a FAANG AI lab.

[Al-Khwarizmi]

> I had a blast and found that teaching helped me understand the fundamentals of my fields at an extremely deep level that I'd never reached otherwise

You spent 5 years teaching a class that, judging from your words, you probably prepared and improved very thoroughly. That is a lot of hours of work. Are you sure if you devoted all those hours to reading textbooks, papers, doing experiments, etc. on your field, you wouldn't have achieved an even deeper understanding?

Maybe yes, but if so, I honestly think you're in a minority. As an academic myself, I like teaching and I do learn things from it, but it's far from the most efficient way to learn a scientific field. If I had a pure research position I'm pretty sure that my research productivity would be better.