Why does Rotoscoping get a bad rap?

[Casual Shinji]

It gets a "bad rap" - you say it like it's unjustified - because it's used poorly and usually ends up looking like crap.

As can a lot of motion capture CGI, which is essentially the same thing, and yet we don't deride that when it is done well, while rotoscoping as a whole is criticized. It can be done well, and it has been done well, but the stigma attached to the practice seems to overshadow the method in a way that MoCap hasn't had to deal with.

I think the difference is that CGI is supposed to represent reality, and traditional animation isn't.

A character like Gollum from Lord of the Rings needs to move as physically accurate as possible so as not to look out of place when acting opposite to the live-action actors.

If a cartoon moves too real it can work distracting and sometimes look even a bit creepy.