I don't want to go to the party for Jon and Eva's wedding anniversary.
Do you think the party will be boring?
Yeah I think it will be.
It would be rude not to attend the event if you think it might be boring. It is good to show support to people who invite you to major milestones in their life.
Why would I go to their boring party? I'm just going to drink and fuck.
If they are your friend you should go to show your support of them. An anniversary is an important event.