I won't say I'm a popular author, though I do have fans. The money I make from this isn't "changing your life" money. It helps pay bills and supplements my income, but that's about it. What does this have to do with Kindle Unlimited? Well, this is still a job and money is still money.
For those who don't know, the Kindle Unlimited program (hereafter called KU) is an Amazon program which allows authors to enlist, and then they pay the authors a certain fraction of a cent per page read. In theory, it sounds great. In practice, not so much. If you're popular and you have a lot of stuff, people who are enrolled in the program read your stuff and you'll get paid a fair amount. If you're not, the pay really comes off as a pittance. I think the current rate is like 0.42 cents per page read. That's not "42", but 0.42, by the way. Not even a cent a page.
The old KU program paid a dollar amount for every time your book was read over 10%. I think it averaged out to about $1.30ish or so, which is not the amount of a sale (a $2.99 book nets the author $2.07 in royalties), but it wasn't, you know, ten cents for a short story. Predictably, there was an explosion of short stories, especially in erotica. When the KU program changed, many erotica writers moved to long form romance. Not all, but a fair few. Authors go where the money is.
I left some of my works in KU, notably the Delilah Devilshot series and the Villainess series, and pulled the others out, slowly. Taking one of my shorts, for example, which is about 6K or so in length, a complete read through is like twenty-five cents, if that, but we'll call it twenty-five cents. In order to make the same amount as a sale, eight people would have to borrow and read it. I just don't think it's worth it anymore, not even for my longer form works. I would rather have more people be able to buy it, than a select few able to read it. I'll still get sales here and there--I do on almost everything now and again, almost just as often as page reads for my older books.
However, the initial boost provided by the borrows/page reads is undeniably useful. Each time someone borrows a book in the KU program, they get a bump in rankings, which increases visibility. So, because of that, I'm going to put my new stuff in KU for the minimum three months, then pull them out and go wide, offering them on a variety of platforms. It's the best compromise I can think of. Whether it's successful or not... who knows? And I don't care (that much). Yes, I'd love to be successful, but more, I'd like to be paid fairly for the work I do. If people like my stuff, they'll buy it. If they buy it and don't like it, there's always the return policy.