There are no other good theories. Most alternatives that don't involve dark matter or dark energy posit that our current theories are wrong on a very large sca

There are no other good theories. Most alternatives that don't involve dark matter or dark energy posit that our current theories are wrong on a very large scale, which we don't have any evidence for at all. On a different note, don't mix up dark matter and dark energy. Dark matter is real matter that we can observe the gravitation effects of. We know it's there, we just don't know what it is because we can't see it. Dark energy is a placeholder for a gap in our current cosmological model. We can model the properties of it, but we can't observe and have no idea in the slightest where it comes from. Neither of these things is a matter of 'making it possible', they're just questions we don't have an answer to yet, and no satisfactory way of working around them.