Use a Helm chart (or alternative)?
When you're writing YAML you can absolutely include from elsewhere (it calls it 'aliases', which is... Well, at least it exists) in multuple places - though annoyingly not from other files.
When you're reading (partially) generated YAML, (e.g. kubectl describe or edit) it's IMO a feature that everything is in its place with no indirection. (And as far as I'm aware this is YAML, not kubectl.)
Well, to be fair, yaml itself doesn't exactly have a stellar reputation, but I've never seen fifty lines of yaml that could convey so little information in any other place.