I'm trying to find reasons to learn XSLT. So far, I've found plently of blogs, articles and so on. Thing is though, they're all pre-2010.

Xslt, while still useful, is not modern and not much new things are built using it as json is replacing xml more and more.

So your not likely to find much new material, nothing has changed :/

We used to use it extensively and enterprise software often use it.

But we have switched to other formats like json or custom formats.

Pretty much what @Voxera said.
Unless you need to exchange information with banks, irs or some legacy system, there are not many reasons why. I already forgot how to xslt anything, haven't had the need for years,

@nbamaral there are similar transformations for json so the concept can be good to know and there are still a lot of xml out there.

And xpath for retrieving data from an xml is used in xslt.

@Voxera
Yes. Although these days I tend use json for just about anything, occasionally I use yml for things that need human handling.
I also abuse serialization on php, storing all sorts of stuff to generic databases, worrying about the db format later.

Reasons to learn XSLT?
There really aren't any.

It's a nightmare to work with and has very few real usecases. Also, XML is (quite fortunately) growing less and less popular.

XSLT is dying (as it should be).
Don't give it CPR.