Would you expect to be able to walk into the middle of a complex technical discussion on a long-running project you're not familiar with, and immediately understand every bit of jargon and shorthand?
Why, then, would you expect to be immediately able to grasp every detail of a complex nontechnical discussion about a long-running project you're not familiar with?
The real issue here seems to be that you're being invited to a lot of meetings you shouldn't be wasting your time attending, because you're not being properly prepared for them so have nothing useful to contribute. Talk to your manager about making more productive use of your time; if they need you to contribute ideas they ought to be giving you the necessary context ahead of time.
Why, then, would you expect to be immediately able to grasp every detail of a complex nontechnical discussion about a long-running project you're not familiar with?
The real issue here seems to be that you're being invited to a lot of meetings you shouldn't be wasting your time attending, because you're not being properly prepared for them so have nothing useful to contribute. Talk to your manager about making more productive use of your time; if they need you to contribute ideas they ought to be giving you the necessary context ahead of time.