1. The Internet is bigger now. Being an average-sized fish in a small pond is not the same as being a small fish in an enormous ocean. Back then, being a professional blogger was actually doable and you could trivially game search engines and ad networks. The Web as a whole has a lot more resistance now.

2. There is already a Wikipedia now; there wasn't one when Wikipedia started.

3. Google wants to have Wikipedia's babies. Google does not want to have your babies.

4. An improvement that would be a great boon to an existing product is not necessarily a sufficient basis for a completely new project, particularly given the inertia outlined in the above points.

Overall, your contention here reminds me of suggestions like "If you don't like the law, go start your own country."