Earlier quoted context omitted.
the downside to xslt is xslt itself, and lack of maintenance of xslt support in the browser. (browsers only supports xslt 1.0 and it looks like even that may be dropped in the future, making its use not futureproof without server side support)
I'm not sure how xslt itself is a downside. It's a pretty natural template language to use if you already know HTML. You don't need more than 1.0 for your simple use-case. e.g. here's a complete example (tested in Firefox and Chrome): Page 1 Page 2 Contact Then here's a page to use it: Welcome to my page Welcome to the page! This is the content Anywhere you want more templates, you add another And now you can use you…
however if you read through the comments there are a lot of people complaining, so they definitely see a downside to using xslt. as for longevity, well, a search led me to a chrome proposal to remove it that was made 10 years ago and ultimately rejected at the time. so maybe you are right about that too.