The value of schema has shifted. It used to be about rich results: star ratings, FAQ dropdowns, product prices in the search listing. Those still matter, but the larger value now is that well-formed schema removes ambiguity when a language model retrieves your page. Accurate quotability is the entire objective of answer engine optimisation, and structured data is how you make a page easy to quote correctly.
The two failures we see constantly are marking up content that is not visible on the page, which is a guidelines violation Google does act on, and deploying schema once without ever validating it. A single malformed field invalidates the whole block, and it fails silently. Nothing breaks visibly, you simply stop getting rich results and never find out why.