Oh here we go again, the FX haters come along to moan. I've got an fx 9590, don't take no notice of them.
RX 580 will be fine for the most part, you might struggle in one or two. But I can assure you now, it won't be as disastrous an experience as they make it out to be. There'll be a bit of a bottleneck but nothing major. And it'll still be fairly playable (I know, I've got a 1050ti with my 9590). And this video also backs up the fact that FX isn't a horrible chip when paired with a big gpu:
It could be better with ryzen or Intel, yes. But is it a bad experience? No. Ignore the FX haters. Get RX 580 and enjoy it.