There is a lot of history to consider with the Gaelic languages (and Welsh, to a somewhat lesser extent).
After the English takeover of Ireland after 1066, the language was effectively outlawed. It was spoken in secret for a long time, which is why it exists to this day, but it wasn’t provided the “air” it needed to grow and evolve into a modern language. For that reason, the language is essentially the same as it was a thousand years ago.
Consider, for that purpose, Old English – and how it looks to our modern eye when written. It’s basically unrecognizable as English. Middle English isn’t much easier to pronounce without serious study.
We’re sitting in 2017 reading a highly tribal, non-Latin-based language from a mostly illiterate culture written with Latin letters based on the sounds those letters made in a mostly Germanic language a thousand years ago.
All the Guinness in the world won’t make that easier, Irish-heritage jokes aside.