I always like to say that SEO (improving your search rank) these days is only a matter of listening for signals from the search engines. Most signals are weak and not worth mentioning.
Buried in the latest Google Search Engine Central Blog is a strong signal about the Sitemap lastmod element, that will probably be missed by most.
it [lastmod] needs to consistently match reality: if your page changed 7 years ago, but you’re telling us in the
lastmodelement that it changed yesterday, eventually we’re not going to believe you anymore when it comes to the last modified date of your pages.
…it’s fine to leave out
lastmodfor those pages.
And when we say “last modification”, we actually mean “last significant modification”.https://developers.google.com/search/blog/2023/06/sitemaps-lastmod-ping
That to me is a strong enough signal. We all know how some of these older architectures are setup to use the same lastmod for all pages. The “we’re not going to believe you anymore” implies a lot. Its saying that Google will rank websites according to accuracy on lastmod, and when your website passes a certain threshold…what do you think will happen?
To ignore this signal and do nothing will eventually cost most websites to loose some ground.
This business of (SEO) search rank is no longer tricky – there are no tricks that work like they did in the early days of search. Now Its a straight-forward job. Stay on the right side of Google’s many “best practices” and you can stay in the top of SERPs.