Google's John Mueller has put down some strong language against changing your URLs for SEO reasons alone. He basically said in most cases, changing URLs will have a negative impact on SEO and that you probably should not change URLs just for SEO reasons.
This came up in two different sites, one on Reddit and the other on Twitter over the course of the same 24-hour period.
John wrote on Reddit "If you're an SEO, and billing by the hour to implement this change, then it'll help your bottom line. Will it help the site? Very, very rarely (if they have terrible URLs that you can't even copy & paste, maybe). Will a change negatively affect the site for a while until it's reprocessed? Probably. Some risk + usually no gain = ... ?"
That is some strong language against changing URLs for SEO reasons...
Then John wrote on Twitter "If you change URLs, you should do redirects per page. There's no maximum number of redirects per site. Also, likely you're shooting yourself in the foot for a while for no visible gain. Change URLs for real reasons, not for handwavy "good for SEO" reasons."
Maybe even strong language against changing URLs.
I have also never been a fan of changing URLs for SEO reasons. In fact, my old stories on this site still have the original URL structure, because I didn't want those URLs to change for SEO reasons. I would often go to great lengths to avoid changing URLs for SEO and other reasons, even if it is more work for my developers.