There's certainly a lot of use of it, but it's painfully obvious when they do so. I think with some more time and practice many studios could make it harder to tell the difference - but it might negate a lot of the cost savings (making more fluid animations rather than the very stiff ones commonly seen, taking advantage of squash/stretch so the movements don't seem so perfect like they were done using computer animation, etc.).

Some shows/movies make it work well enough because there's things other than the animation that keep you watching, some use it for walking/transition scenes where it's easier to "blend" it in since it's background to the dialogue most of the time; but I really wouldn't say the "2d animation look" is even close to being achieved in many cases right now. Again, not because I feel the tooling is incapable of it - but because doing it right would nullify the cost savings and defeating the purpose.