They are going to have to decide which 25 people to uninvite, and not only be uninvited but lose their money. Where do you start with that? The wedding will probably be the biggest thing they have done if they are young, and will have cost money. They will have planned it and dreamed of it. Of course they are annoyed to have it cancelled, particularly when it has been postponed twice.
I don't know why their irritation upsets you so much. If they were expecting exemption from the regulations, or campaigning to change the law I could understand better, but if they are simply expressing their feelings to a reporter who probably contacted them with a 'How do you feel now that your long-standing wedding plans have been disrupted?' type of question then I think their response is understandable.
Whether they should have booked it or not is easy to see with hindsight, but advice that needs time travel is never welcome
. My son is getting married in the Spring. The ceremony is just for immediate family, so unless there is a total lockdown or travel restrictions it will go ahead. The party is a week later, and is a much bigger affair. They got engaged last July (ie 2020) and May 2022 seemed ages away when they booked the venue. If it can't go ahead they will be very disappointed, but can you honestly say that they were irresponsible or foolish to pick a date nearly 2 years after the engagement? It is in the UK, but some of their guests will be travelling from abroad.
Covid is unpredictable, and things might not go ahead as planned, but I don't think they should wait forever to get married in case there is an upsurge in numbers. Life has to go on, albeit with an eye on the numbers and a readiness to change plans at the last minute. I can still spare a lot of sympathy for that young couple, though.