Here's three facts: water is wet, the sky is blue, and for every sensible and qualified astrophysicist, there's at least a thousand non-physicists who claim to have an idea How It All Works.
Unfortunately, I'm one of the latter, a non-physicist who thinks he's got the next great idea. Here goes:
Dark matter - no. We already know that spacetime is affected by gravity, so we know that the "fabric of space" - for want of a better term - can be distorted. If the consistency of that fabric is not 100% uniform in all locations at all times, then the fabric of spacetime is *not* uniform. If the consistency of the fabric is affected by microgravity - such as the ever-so-slightly-higher gravity within a galaxy as compared to that of intergalactic space - then this may better explain the formation of galactic structures. What's more, if the consistency of space within a galaxy is "thicker" than outside that galaxy, it may provide a solution for the galaxy rotation problem.
Dark energy - no. As the universe expanded (and continues to expand), what is outside the volume to which it has expanded? Of course we can't know, but chances are pretty good that it's *empty" - even emptier than intergalactic space. If that is the case, if the space outside the great bubble we call the universe has a vacuum stronger than the vacuum within the universe...and vacuum, being vacuum, sucks. It not only pulls at the expanding bubble of our universe, but as the bubble expands, more area is exposed to that utterly-perfect vacuum...and that's why the closer to the edge of the universe we look, the higher the redshift. It's not "dark energy" pushing us apart - it's that perfect vacuum at the edge of our universal bubble *pulling* us apart towards that eventual Big Rip.
*ducks to avoid the slings and arrows of outraged physicists who are sick and tired of non-physicists taking the First Amendment a little too far*