The site could for sure benefit from a few SEO tweaks, but even then I'm no confident as I used to be that changes immediately equal results

The last year has been tough, even if you are doing the right things, SERPs are being slammed with AI content and Google doesn't yet have an answer for it, and any update they make hits sites it didn't intend to hit.

I've never seen it this bad, SERP volatility hasn't been this high in ages