Largest Contentful Paint should land under 2.5 seconds, Interaction to Next Paint under 200 ms, and Cumulative Layout Shift under 0.1, all at the 75th percentile of real visits. Field data (what Chrome users experience) is what counts; lab scores are diagnostics.
The common failures are consistent: unprioritized hero images and font swaps break LCP and CLS; heavy JavaScript breaks INP. Beyond rankings, stable fast pages are also easier for crawlers to render — slow, shifting pages get partial reads.