Yes — it's been in use for years, with some examples here:

https://www.investopedia.com/terms/a/activist-investor.asp

It's important to remember that in common usage “activist” doesn't mean anything other than trying to change how a company is run — there isn't the connotation of social values or similar which the term has in common usage.

Bloomberg and CNN did, last year:

https://www.bloomberg.com/news/articles/2020-02-29/singer-s-...

(previous link paywalled, outline: https://outline.com/gxqsh2)

https://www.cnn.com/2020/02/29/tech/elliott-twitter-jack-dor...

It's a real term used in the finance industry to refer to investors pushing for changes that often run counter to what current management/board wants.

Why do you think it's a poor term?

I think the term has been around since the 80s.