An idea does not need to be a super size or all encompassing one. Entrepreneur may look at companies who have created great products and then derive the idea that is close to the most successful idea present in the market.
There are many social media networks that look like each other. Also there are hundreds of soap brands, shampoos, cars, apps and many others. Without a good branding , it would be hard to tell one from the other.
Entrepreneurs often have the notion that to win the market , they have to create something big, something original. In my opinion, original maybe but big definitely no. If one does not want to rely on others to fund them or they do not want to engage in direct competition with the leader in the industry, they have to neither be wholly original nor big.
When a product rises to become famous, competitors create similar products. However these products are not very different from the original. Thus they never take off the way leaders have done.
Spot the trouble
What the entrepreneur needs to do is to find chinks in the armour i.e. areas where the leader is weak, unwilling to respond ( because it is looking somewhere else, for example maintaining its market share) or just careless. This is how entrepreneurs have been successful all throughout. They spot inefficiency , build a product around it and become big. This does not need big budgets, however it may need big and deep thinking.
For example, big social media networks till now had a bad track record of managing user privacy. A good competitor would have concentrated on best quality privacy control. They would also have a paid model instead of a free model. All they had to promise was that they would not ever touch or look at the data of their customers.
Would people pay ?
Yes, it is a niche market and hundreds of people who want to connect but do not find an alternative, that is cool enough to rival Facebook. That would have been some threat to the leader. ( There , I gave you an idea to think about).
To win market, you need to spot inefficiencies which will always exist no matter how perfect world becomes.