Ireland without an teanga is a country without identity
This has nothing to do with the survival of the fittest, but is a matter of policy. The Dutch language has thrived in Belgium since the normalisation of its use in public life there was achieved. The same Dutch language is dying out just across the border in Dunkirk, where it was the majority language for centuries, because of its being banned from official spaces by the French state.
Speaking more than one language is normal. An English-only mentality is costing us export markets and jobs. Our negativity toward speaking Irish saps morale. We need to open our minds to the wider world.