All the records were destroyed
This is not true. While the explosion at Four Courts was very unfortunate, it did not destroy all records. I have to admit that when I saw what was included on the 1841 census, I could have cried because it would have been such an amazing resource for all of us but there is no point in dwelling on it.
We lost the O when my ancestors took the soup
This is not true, many names were Anglicized over the years beginning as early as the 1600s when Protestants led by Cromwell devastated the population and enforced Penal Laws.
They changed the spelling of our name at Ellis Island
This is another fallacy. I can show that the spelling of my own ancestor Geoffrey Donoghoe is spelled differently on several of the baptisms of his children in Ireland. Since it became Donahue in our particular family and no ancestor came through Ellis Island, I guess that dispels that!!
Keep in mind that many of our ancestors didn't read and write and would not have known how to spell their name. Whoever wrote it down, would have spelled it the way it sounded to them with a distinctive Irish accent.
When it comes to the records that exist, Parish Records, Tithe Applotment and Griffith Valuation are the most readily available and offer a place to begin.
I hope this gives you just a little more hope that Irish genealogy while difficult, is not impossible.