The docs are just explaining how method resolution order works in ruby (i.e. explaining method_missing but not saying you should rush out and use it).

Personally, I've never used method_missing. Might have missed opportunities to write clever code, but I'm super happy being boring and explicit.

Tangentially, I've only used meta programming twice. Both where the alternative was cumbersome, and it was unlikely to cause confusion.

Ruby gives some exotic tools but doesn't force you to use them if you prefer not to.