Google shows really old dates in SERPs (from 2008) - how do I get those dates removed from Google?

I have a problem on my site in that old posts show really old dates in the Google SERPs, even if those posts are still relevant and have been updated since they were created. For example some posts show dates from 2008 (when the posts were first published). I think this seriously hurts my CTR in Google. When I have both "datePublished" and "dateModified" on my site, Google will just show "datePublished" (which are the really old dates).

A couple of months ago I removed all dates in the code (including "datePublished" and "dateModified") to solve the issue. However, this just makes it so that NEW posts (that we have published after the date we removed "datePublished" and "dateModified") show no dates. The OLD posts (from 2008 etc) still show the old dates, even though the dates don't exist in my code and Google has had plenty of time to re-crawl my posts. It's like Google is saving these old dates in their database, and I can't get them removed. Does anyone know how to get them removed? If not, what do you suggest that I do to get Google to remove the dates or add new more relevant dates?

I guess I could add "datePublished" and "dateModified" back to my posts and change all of the dates to for example January 1st, 2022. But I feel that this is a large risk in terms of SEO, as I don't think Google likes that you alter the date information in that way, and I think it could cause lower rankings (now or in future updates). I therefore don't see any good option of solving this, and would appreciate any suggestions. Thank you.