Using a Black Magic camera means your film will be incredible, and using anything else is a waste of time.
I shot recently on a 5D with CP.2s and I can tell you in the final cut it will look better than anything londonfilmmaker, with 0 experience and knowledge, could shoot on a Blackmagic.
As far as being 100% satisfied with your work - I work with professionals and we shoot on high end cameras. There are two films I shot over the past few months currently goign out into the festival circuit. I'm not 100% happy with them. There are some shots that don't quite work they way I'd have liked, there are some colours that aren't quite exactly what I wanted, there are cuts that don't quite gel the way I though they were, and the Sound Design isn't mixed as well as I imagined.
That doesn't mean it's a bad film. I'm simply over-critical because it's my own work and I can be. I haven't posted anything in the screening room because of festival rules, but eventually I will and you can judge for yourself.
If you do nothing, you do nothing and you learn nothing. The first couple of films I ever made were absolute crap, but you learn from your mistakes. Film School is what launched my professional career, and I certainly made mistakes during my time, but you learn from them. Mistakes I made during school are mistakes that i have since not made again in the professional world.
And a camera body has nothing to do with how a film looks. The biggest contributor from a DPs perspective to how the film looks is lensing and lighting. After that, a camera body is more or less like a film stock - they all have their different characteristics but are all perfectly fine for use on any movie. Overall, Prodcution Design is probably the biggest thing lacking in most low budget productions. Production Design can make or break a film, and can be the differentiator between amateur looking and professional looking. There's no point having the best lenses and best lighting if there's nothing in the shot to look at. I rely heavily on the Production Designers to dress the frame and make it look great.
That, and proper colour correction I think are the two biggest things - I've seen professional colourists take footage shot for a film on Alexa, 5DmkIII and slow-mo in FS700 and grade them so you can hardly pick the difference between the three, especially on anything smaller than a cinema screen. So many T2i movies either aren't colour corrected at all, or are crushed too much - too much contrast. Plus, usually they're shot without keeping things within the range of the camera - if shooting on a DSLR and there's an inside scene with a window, I'll gel the window with ND1.2 so we can see outside, and stick a light bouncing in the interior, so the window doesn't blow out. So many DSLR projects just let the window blow out, or let the shadows clip.
Oh, and sound, sound is a huge component that often gets overlooked.
However, with all that said, films that exhibit these things are not necessarily bad films, and are often completely watchable. I watched Like Crazy, where there were shots and areas that were under-exposed, there were shots and areas that were over-exposed. The whole film looked like it was shot on a 7D and withuot a huge budget. But I got sucked into the movie and loved it. And that's why it got distribution - it was shot on a 7D (admittedly with Ultra Primes), but it was distributed internationally in cinemas. As long as a movie is altogether watchable, it's the story that really matters in the end.