Sure, some people overblow the difference between various bodies, but people were also saying the same things a 8 years ago that some people in this thread are. That differences in camera body don't matter, that sensors are 'good enough', etc.
Would anybody use a body from 2004 now?
Lots of incremental improvements add up over time to a huge difference.
Can somebody who knows how to shoot go out with an original rebel and come back with great shots? Of course. Can somebody who knows how to shoot get more out of a modern camera than an original rebel? Absolutely.
Does the D800 blow the 1DX so far out of the water that it's not worth owning Canon? No, I don't think anybody would even think about claiming that. Does the Nikon D800 have a cearly superior sensor? Yeah, if you claim otherwise you're just ignoring objective facts. Is it such a difference that somebody who knows how to shoot can't get around it? No, I don't think anybody would claim that either.
Also, people should quit being so defensive when their camera gets outscored in objective tests. Do I have the greatest body in the world? Nah, not even close. I'm still on crop frame. Do I feel some need to try to marginalize or discredit objective tests because of that? No. The tests are good if you know how to interpret and what they do, or more importantly don't mean. Making sort of silly sarcastic comments about 'oh, going to sell off all my canon gear you guys' kind of indicates a defensiveness. If you really didn't think that DxOMark test results matered, you wouldn't get so defensive about it. The 5DIII is a great camera. You know that. The D800 has a little bit better sensor, so what? If you're a Canon guy (or gal), don't worry about it. Do I give a crap that the 70-200 MkII f/2.8 L wipes the floor with the Nikkor f/2.8 VRII? not really. Sure, it'd be nice, but I dont feel a need to either freak out about the tests and get defensive about it. Each side has their advantages. Just accept it and don't begrudge the other brands objective advantages.