Oh good grief. Its like attributing the snubbed Markle attitude onto anyone not invited to the ceremony.
To be honest, I don't think those that weren't invited in spite of a minor bloodline connection would feel left out, snubbed, or anything other than happiness that the wedding did happen. Some people are just mature that way.
It is not a matter of bloodline connection, but one of respect for the Royal Family as an institution. The third cousins weren’t invited either to Charles and Camilla’s blessing, but what is shocking in this case is that they are not invited while pop stars and celebrities with superficial connections or no connection at all to the groom are.