e.g. Google could make Google Analytics compliant (likely by, as you say, housing EU data in Ireland), but it seems that currently they are not.
Also, beyond the physical colocation of data, there are ancillary issues around data being readily accessible (either by internal engineers/agents or external authorities) from outside the EU to consider as well.
https://en.wikipedia.org/wiki/Microsoft_Corp._v._United_Stat... (2016) and https://en.wikipedia.org/wiki/CLOUD_Act (2018).
If so, it might end up in court again, and we'll have to see how that precedent gets set out. Will be curious to see how this plays out.
I suspect the issue is rather that Google Ireland are not in fact exclusively housing EU data within Ireland (or the EU in general).