...and as a result a hefty fine under an unrelated law should be levied? Europe is and should be a place where laws are more than just tools with which to punish disfavored parties. If the double Irish should be illegal, then make it so, and hold on tighter to the straight and narrow path.

Double Irish is treated illegal as "illegal state aid". Would it be legal in US, if Delaware decided to give some foreign company (registered in Delaware) only 0,1% tax on everything they earn in the US? I thing the federal court would rule such "state aid" as illegal...

Which is legal. The Apple case was about "illegal state aid" of all things.

So either EU is grossly incompetent to stop such thing at EU members level or they just think acting against individual companies will generate more fireworks and public support.

It's more that the EU doesn't have the political will to do what is perceived as the common good here.

Ireland has a selfish interest in attracting tech companies, and the rest of the EU can't bring enough political leverage against them to change the legal structures that make Ireland preferable for headquartering.

Equally Luxemburg is another EU location abused by corporations for TAX reasons. Ironically it was set up By a Mr Junker ages ago, who then went on to run the EU and has made much rhetoric about TAX avoidance and yet managed to do nothing to fix, in-part a situation he created. Which given his knowledge and experience in the matter, you would of thought he was ideally placed to fix now. He has not alas.

No political will? What about the EC's order for Apple to pay 13B € in unpaid taxes?

Ordering an US corporation to do something is entirely different from making a member state change their laws.