If Google rewrites title tags, this is not a sign of problems with the quality of the site or page. As Google spokesman John Mueller explained on Twitter, it happens that some good sites have bad titles, and bad sites have good titles, you should not treat them as quality signals.
This is how he answered a question asked by SEO expert Lily Ray:
“If Google rewrites titles for 60% of pages, can this be perceived as a potential issue with the quality of the entire site?”.
As you can see, if Google is zealously rewriting your title tags, at least you can be sure that this is not due to site quality problems and will not affect its ranking in any way. This, of course, can affect the CTR of the site on the issue, but there can be no sanctions from Google for this, says SearchEngines.
Note that the Search Central documentation states that title tags are automatically generated by Googlebots, and the main reason for changing them is to make it easier for users to understand if the page contains the information they need.
NIX Solutions reminds that Google launched a new system for creating page titles, which caused a wave of criticism from webmasters, in August 2021.
According to a Zyppy study, by January of this year, Google had already rewritten more than 60% of all titles.