honestly, I'm not sure if it will such a huge thing as expected.
Edit: As you see, those are just the lab results. I have finished the work about 2 weeks ago, still more than 200 "bad pages" in Search Console. No changes there.
I tend to agree with you. So, Lets look at Google's past supposed influencers.
PR (page rank - the higher number the better) was a huge thing back in the day...
Though, when it came to the crunch, sites with a PR1 were, almost always, outranking sites/pages with a PR6.
G+... Aside from the social media aspect, it was also supposed to FIX content scraping, to stop nefarious sites, outranking the copyright holder's site content. Using the meta data code tags for "Author" and "Publisher" (verified by Google with the owner's site/s), sadly this also failed.
Heaps more fails, too long to list.
Point in question... How many sites are operated by non-tech folk?
If core vitals are going to make a "massive" impact on G search results, and your not tech/code savvy, then your screwed.
NB - There's only so many things a WP plugin can fix. The rest, you either need to know how to code, or you pay a coder.
Granted this is Google we're talking about. But even for them, I can't see, they'd be OK with pissing off millions of people. Not good PR
Edit:
When site loading loading times became a factor, one of my sites was host here in AU. However, no matter what I did, just could not lower the server responses times, which, according to G, were taking approx 1.5sec too long. Turns out, G were running these test from the USA. The alog was NOT factoring in the number of hops required for the round trip from USA to AU.
Finally because of sheer frustration, I moved to a USA server. Same specs as my previous AU server. Surprise, surprise, my response times for G were now lightning fast, and not causing any speed issues.
In closing, there are just so many factors which can negative impact a site. This is why I don't see core vitals being a worry.