I also recently saw Banshees, or tbf I gave up halfway thru bc I thought it was boring and unfunny. Probably the last I'll spend time on a McDonagh project. I said the same thing after Three Billboards - possibly the most clueless European take on America I've ever seen, which as you all would say, is going some - but this one has good press, Brendan Gleeson is always great, I like very dark comedies, etc.
But yeah, unwatchable. The cast are doing their best but the jokes are flat, the metaphors are as subtle as a hammer to the face, and even as a foreigner you get the strong feeling that his view of Ireland, especially old-timey tiny village Ireland, is about as realistic as his take on middle America. Also, both his dialogue and overall story stricture are extremely stagey, a la Mamet but worse, in a way that doesn't translate well to the screen.