Google's John Mueller said again that using hreflang will not help you rank better and does not change rankings for your site. All it technically does it replace the URL that ranks already with the regionally appropriate URL in Google Search.
John said on Twitter when asked "Is there any chance someone would see a rank increase after implementing hreflang?" John replied "No. Hreflang does not change ranking."
No. Hreflang does not change ranking.
— 🐐 John 🐐 (@JohnMu) March 10, 2022
John said this before in 2016, so this is just a reminder. Here is what he said in 2016 in a video hangout on Google+ at the 2:29 mark into the video. He said:
Kind of think think if you didn't have those local pages would the dot-com pages rank in the local search results? And if they would rank then we'd like to swap at the URLs out against the appropriate local versions. So if if you have a website, I don't know that, that's targeting furniture and you have a UK website and it doesn't show it all in in France for example, then just setting up at the href lang with completely new pages for France wouldn't change anything because we wouldn't have anything to swap out. It wouldn't be that your UK page would be excessively ranking.Another hand if you have liked for Germany and Austria where the the content is German both the same and your pages for the country of Germany happened to rank in Austria then that would be something that we could swap out.
Forum discussion at Twitter.