One of my biggest issues with php was the number of imports and file reads involved. It made running something like wordpress _really_ slow on slow disks or over nfs. I don't remember apcu or opcache helping much for that because I think it still did a stat on every file iirc.

For single-file php apps or just not using a big framework, it's not really a problem.

You can configure opcache to never stat unless it's reloaded