My opinion on the matter, after a few nice and not so nice oval races in iRacing, is the following:
Driving on ovals is as boring as it gets. Racing on them in close competition however, is (sometimes very!) exiting, although very different from circuit racing.
There's no genuine challenge in finding your marks and being reasonably fast on an oval, the 'fun' comes in when you're doing it for 30+ minutes straight constantly side-by-side. Having said that, I draw a lot of pleasure in learning a track and finding personal improvements after hours of practice and reflection; so the whole oval racing doesn't appeal to me as much.
I wouldn't instantly dismiss it as 'boring' anymore though, although admittedly I do still find it hideously boring to watch.