In many companies, it is frowned upon to decline meetings to which you are invited as a 'required' attendee. Likewise, it can be seen as rude if you repeatedly leave meetings which you don't think are a valuable use of your time.

Useless/overlong meetings seem to be a consequence of poor middle management and/or just the general structure of large corporations where lines of communication and hierarchies of responsibilities are complex.

What I do personally is to always ask for an agenda before accepting a meeting request. It's not rude to request one and can help focus discussion or see where you can add value.