An Irish person should perhaps answer this but to my knowledge, Irish is only a symbolic language on Ireland. I doubt that it is the mother tongue of anyone these days. If it is, then the person is fully bilingual with English as their second mother tongue, spoken with no accent other than the normal accent that Irish people have when they speak English. I think. I am almost sure that has been the case for 100 year.

The thing that is different is that some Irish and Scottish people speak English with a very strong accent, so you almost think it's a separate language.

But the Welsh, Scottish and Irish languages are kept alive artificially, by people who love them and have strong nationalistic pride, and with national and EU grants.
I have asked Irish people a few times if they can speak Irish, the answer is always "no" only a few words and phrases. Many see it as an inconvenience, because learning the symbolic Irish eats up school time that they could spend on French, German or Spanish.