Maybe it's just me, but I can't think of anything more depressing than doing the exact same thing my entire career. I think the need to stay current is an advantage of the tech industry.
Equally depressing is the thought of giving up all the ground gained and lessons learned every time a new fad takes the stage. Watching the same mistakes made over and over, only moreso... That's depressing.
I think this as much as anything contributed to my burnout. Burnout is maybe too strong a term -- disillusionment is maybe better. I see younger devs getting excited about something new, and to me it's just "yeah I've seen this movie before." The novelty factor is just gone -- work is simply not that exciting.
The thing is, though, that there are probably new technologies (or at least technologies that are new to you) that you'd probably find interesting.
The key is finding them and giving them a chance.
When I was young I hadn't heard much of Lisp, and what I did hear didn't sound that great (Lisp was old and maybe it was great back then, but technology has advanced so much, I thought, that it's probably not worth bothering about)... but when I did finally learn it I fell in love and wished I'd learned it much, much earlier.
And it wasn't just a copy of something I'd learned before, as were many other technologies that I'd learned.
That said, when you are seriously depressed or burnt out (the two go hand-in-hand), it's tough to find anything interesting, even things that you'd normally be fascinated by.
Different strokes for different folks. I would go bananas having to keep up with the totally unnecessary technology treadmill: re-skilling again and again forever, on new hotness technology fads just because they’re new.
“I can’t wait to rewrite this legacy software in Rust!” - said not me.
There are differences in the "totally unnecessary technology" treadmill. If some employer says "I want to build this product on Azure. I heard it's hot. Oh and use Mongo DB too, and use Go" when it would be sufficient to just spin up some sqlite-backed simple thing in Python on one low-end colo box, it's still unnecessary technology, but I'd definitely enjoy learning it. Those pieces of tech would also be good resume fodder for future jobs too.
When I have to learn some NIH-based technology that poorly copies something widely used (e.g. the place I currently work at has some custom language to generate "template instantiations in C" and some half-assed hideous clones of protobufs and grpc), I can't bring myself to care or really do my job.
Thank goodness this pandemic has made it easy to spend large portions of my day on leetcode / the CRLS algo book without anyone looking over my shoulder so I can get outta here!
Using old technology does not have to mean doing the same work. I write a lot of C for embedded systems, but it remains fun and exciting despite the language being 40 years old and the chips I program 15 years old. The systems I create are new.