You
What actually matters for a small static site in search?
ChatGPT
Three things, in order: the title and description, the words the page uses matching the words people type, and links from places that already rank. Everything else is polish on top of those, and no amount of markup compensates when they are wrong.
You
How do I know when it stops being worth it?
ChatGPT
When you stop noticing it. If it has not surfaced a problem in six months, it is either solved or it was never the bottleneck you thought.