There are two main factors that differentiate a startup from a big business:
Big businesses aren't "agile" like startups because they have a history of making money. Think about this for a minute. The reason they are a "big business" is that they found a formula that "works". Maybe it doesn't work as well as it used to, but it still works. Making dramatic changes to how they work puts their existing model at risk - which is frankly foolish for 99% of large companies. Like most things, this is both good and bad for startups. It's good because it means you can try new business models, tackle new opportunities, and do things "differently" than big businesses. It's bad because you don't have a history of knowing what works or of servicing people in that industry. That's why its both risky and exciting to be "a startup".
The second factor is resources, and basically big businesses have "a bunch" and startups "have none". If you're going to compete with big businesses, you can't start by going "head to head" with them - you have to choose a single aspect of your business that you can do better and do it the best in the world.
To really drive this point home, consider what it takes to run a business (broad strokes):
You can't be better than a big business at all of these functions when you're 1-5 people with very little cash. It isn't possible.
That means you're going to have to prioritize and accept that you are mediocre - or even bad - at some of these things until you can get more resources. But to survive and grow your business, you need to be a lot better - often 10 times better than your competition at exactly one thing.
In order to understand your "bench strength", use the file attached to list all of your team members (including yourself) and their responsibilities - what they actually do. Then, beside each of their responsibilities, rank how good they are on a scale of 1-10 where 1 is incompetence and 10 is "best in the world".
(img src: //i1179.photobucket.com/albums/x400/photoshop-tutorial-in-bangla/chobirdokan/143.jpg)