There were no technologically advanced Indo-European society in Central Asia before Indus valley civilization. The most advanced would be the Mesopotamian which is again closer to Dravidian. Indo-Europeans were nomads not sedentary population which you need to build technologically advanced civilization.
The Basques speak a language that's clearly at least 10,000 years old. The Irish speak a Celtic language imported from the Danube (which means the Spanish records are more reliable than the British records regarding the movements of that particular leadership elite).
So, yeah, the Basque languge is today an "isolate" but how'd their genes get spread all over Europe, particularly to Ireland?
The Galician (Spanish) record says the predecessors of the Irish elite came from the Danube through the Black Sea, through the Mediterranean to Galicia in Spain. From there they mounted an attack on Ireland and took over ~ taking with them, of course, their Basque servants (and slaves).
The areas we know which were subject to Basque culture were far more extensive than in modern times (you just dig up arrowheads and potshards). The area has been repeatedly invaded by Indo European speaking illegal aliens for centuries.
The Basque people adapted by moving or learning a new language. However, they appear to have been part of the original population that survived in the Western European Refugia during a period of peak Glaciation in Europe ~ which cut them off from everyone else.
Concerning who was or was not sedentary, the Indo-European speaking people were agriculturalists ~ not nomads. They had horses and iron.