What Kim said! Tailored fits shouldn't feel uncomfortable, if they fit well (or at least I won't buy anything that does feel uncomfortable, even if tailored) -- so I don't experience the difference between those and fluid or oversized fits as so extreme.
I do think the key to this is wearing tailored fits a bit looser than some of us might have been wearing them over the last few years.
Example: I tried on an old BR no iron shirt the other day. It fits me, no question. Fits well, in fact...but it's a very tailored fit. More tailored than I typically wear now, and probably more tailored than I typically wore back then, too -- since I pretty much always went for a bit of extra room in my tailored fits.
And all of a sudden, it felt altogether too tailored. Not "uncomfortable" per se -- but the kind of structure that made me conscious that I was wearing it, all the time. None of my current tops are cut like that. Not even the tailored ones.
Also -- there's a difference in comfort between a silk shirt (even a fluid fit one) and a sweatshirt. Not in terms of how it feels, but in terms of what you might feel comfortable doing in it. I'm not going to roll around on the floor with a muddy dog while wearing my silk shirt. I'm not going to pop it on over my running clothes after a sweaty run!
I guess Janet hits on this aspect with the comment about casualization.