I am a wedding hater. Not because of the B+G at all (except in rare circs lol).
I do not like weddings, hate them in fact. Sorry about that. Seems like a summons most of the time rather than an invite. And for what, a long drive, and overnight, money money money for a few hours of drivel and ooh look at the dress isn't it Gorgeous. And sitting with people you don't know and such a long boring day really. Anyway, I have issues about weddings as I am sure you have guessed!
So I am with the OP on this one. Do NOT go. Do NOT give any lame excuse.
I usually respond with Hi X and Y, thanks so much for the lovely invitation, but we cannot join you for your special day due to prior committments we have on the same day. Hope you have a wonderful time. Love, flowers.
And enclose a cheque for the wedding pressie. All happy! Whew....
OH is the same. And it's the same for his side of weddings too.
We of course will attend close family - nieces and nephews are the last line though!
It is so liberating!
I really don't do anything, or go anywhere I don't want to anymore. I'm talking friends here. Family is different, we have a blast. (Most of the time!)