(idiomatic, anime and manga fandom slang) To be so immature and unprepared as to have no hope of achieving an accomplishment.

It is possible to learn new things, at any age; follow your desires and dreams.

(UK) It is suspected that, because someone is insisting too much about something, the opposite of what he or she is saying must be true; a hit dog will holler.

If too many people participate in a task, especially in a leading role, the task will not be done very well.

(idiomatic) To seek to have two things which are mutually incompatible (such as eating a piece of cake and yet still possessing that piece for future use).

Too many leaders or managers and not enough people doing actual, useful work.

Alternative form of too many chiefs and not enough Indians

Alternative form of you're never too old to learn

(idiomatic) Alternative form of have one's cake and eat it too

Alternative form of too many cooks spoil the broth