I assume you're explaining the fear, because the opposite is true. You'd be lifting a barrier. The barrier is you doing all the legwork while having all the institutional knowledge. Business cannot afford you doing the legwork, you need to be mentoring and delegating.
Completely agree. If you never say that you are at capacity you become the dumping ground for work that other people should be doing.
It doesn't have to be a complaint. Just put a higher fibonacci on your work or whatever. Don't see how it's a problem if you're honest from the get go.