It's fascinating how the only people defending Canon's latest releases all own either a 5D3 or a 1DX, and as such, are probably not going to buy a Rebel. If yes, only as back-back-back-back-up body.
Maybe your perspective would be a bit more accurate if that was the only Canon camera in your budget. Sure, one can switch to Nikon, but it has a cost to rebuild a lens kit, and money is the problem to begin with. Otherwise we would all buy a 5D3 and a D800E and lots of top glass and be happy ever after.
I bought a D600 and I'm building a set of lenses in F-mount. I didn't like it. Switching brand is always some sort of hassle and economic inconvenience. I could afford it and it worked very well for me, in the sense that I'm very satisfied with my purchase. But I understand that not everyone can afford to do so. This doesn't make them a bunch of childish whiners. As a matter of fact, I would hardly advise anyone to buy a 700D over a D5200.
I don't think people would argue that Canon needs to improve its sensors, but that takes time -- years. Engineering takes years, tooling takes a year or more. What is coming out has been planned years ago. I think it's pretty clear Sony/Nikon caught Canon off guard. It may take a couple more years before you start seeing the changes you want.
Unfortunately, the Rebel line is refreshed yearly. It's also unfair to expect the Rebels to feature the newest and highest IQ sensors first -- I'd expect those to be in the xxD and xD lines first. And history bears that out. Over the next 3-4 years, the Rebels would inherit most of the features of the xxD line and the cycle starts again. IFF the 70D comes out with a new 24MP sensor, then the Rebel would get that in the future, not now.
Does Canon deserve to lose market share in this market? Yes, if its competition offers superior value
to its customers, and that value is not just the body, but the whole system including lenses. But Canon also knows that a large segment won't get anything beyond the kits lens(es), so it might not lose many until it can get its problems fixed.
Canon's FF offerings were all refreshed last year. This year and next will see the APS-C lines get refreshed. The future Rebel upgrades will be clearer once the 70D is released. If you can't wait until then, choose the best system for you based on your time-table. I'm sure Canon would rather have you as a customer than lose you to a competitor, but it can only move as fast as it can. You make your choices based on your needs and what the market offers. Complaining that Canon doesn't meet your specific needs/time table won't change a thing. Individually, you or I do not matter. A single person is not a profitable market. Thousands/millions of people compose a market.