I tend not to get too cynical about the publishing markets anymore - after all, publishers simply reflect what people are buying.
The fact that Robert Jordan, Peter F Hamilton, and George R R Martin, have been writing epic series that people love isn't the fault of the publishers - in fact, that they may be more open to epic works from newer authors I think is great news. Especially when a few years back when shorter novels were more the norm, it seemed ridiculous to feel you'd have to chop out parts of the story, just to have a smaller word count. So it seems like a more positive progression that larger wordcounts may be more acceptable.
I also tend to get cynical about looking back at what writers did in other times, and using that to suggest modern markets are wrong. My impression is that writers of other periods wrote for the markets of those periods, and the works they developed were precisely because of market concerns, not artistic ones. Same for the modern writer in the modern markets.
Of course, the point about the old gothic tomes may be a pretty salient point - but it's also worth recognising that traditional publishers are coming under increasing competition from smaller publishers, so maybe the checks and balances are better oiled. If not, if the big publishers misjudge matters, you can bet there are smaller publishers keyed into the internet who can take advantages of gaping markets.