From what Intel put out in marketing materials, even at 14nm they had a very unreliable process with DUV. So, it might not be economical for the type of IC produced in these factories.
TSMC's DUV 7 processes are reportedly very good.
And I thought Intel's 14 was good too (after some ramping), which is why they stayed on it and iterated on it for so long, it was the 10nm process they had so much trouble with and the problems there are not generally reported to be with lithography but materials (cobalt, among other things, which they dropped in later nodes).
So I'm not sure what you are trying to argue. DUV has _proven_ to be economical down to about 7nm.
This is really more of an engineering problem, you need more cycles for quality and reliability. But it's not something unsurmountable. Intel had no reason to try hard enough, Intel is never going to get sanctioned.
'Necessity is the mother of all innovation' might come to play here. If it comes down to living vs dying, people go to no ends to make things happen.
The nm measure is a marketing tool. Intel nm is 'larger' because they were measuring gates differently.
I only take nm claims as comparison of products of same company.