Given the numbers of Irish in this country, the EU forcing them (us) all out would be kind of catastrophic for both economies, don't you think?
There are more Irish in England than there are in Ireland
Most will have done their time to be able to apply for British citizenship which many are now doing, as they should have done as soon as they could apply as it is only an agreement.
The UK doesn't require the Irish to have worked, so unlike the EEA citizens, it is an easy process for them as long as they haven't served time in jail, ever been a sex offender in any country, kept committing offences in the UK, kept running up parking tickets (lack of respect for the laws of Britain) etc.
Ireland saying to the EU that this is so vital to Ireland, that if the EU stops this, they might have to leave the EU too.
However, since that agreement over 100 years ago, Ireland joined the EU with the UK and now has free movement too of course and their citizens can go to the other 26 countries on free movement. But the EUs free movement, as you have read, is nowhere near as generous as Britain for them.
The Irish government have the problem that this is only an agreement from Britain, whereas if they remain in the EU, they will always have free movement. The UK will always have visas for those that have the skills the UK wants and will most likely have temporary visas for the low skilled, as the foreign secretary has already talked about.
But Ireland is a small country in the EU with a small voice in the EU once they lose a big payer like the UK. At least Poland, who also relied on the UK in the EU, have joined forces with the so called Visgrad Group, while venting their anger towards their ex PM Donald Tusk by trying to stop him getting re-elected as one of the EU's many presidents.
I had planned on applying for British citizenship just as soon as was possible, as had my daughter.
As you knew before you moved, that is unlikely under EU laws as that needed at least 6 years of EU laws before Brexit. It's a case now of waiting to see what is offered.
At least you arrived knowing how the 2004 EU Directive of free movement works to make sure you stay legal in the UK at all times, have no intention of not having legal status in the UK and have no illusions.