Are you truly insulted or it’s just the principle? Do you have as much to do with this baal simcha as the rest of your co-workers? Were they invited to the full wedding or just the chupa? Weddings are expensive and it’s come to a point where people stop inviting people “just because”.
I had a neighbor complaining to me how much his wedding was going to cost and I told him, “why do you have to invite anyone you say hello to? You don’t have to invite me just because I’m your neighbor”….and you know what, He didn’t. and I was very happy not to have to shlep out of obligation.