There's a big difference between apps and restaurants. One chinese restaurant can only serve so many customers, but one well made website can serve the entire market, making other solutions of lesser quality almost worthless.

That being said, I agree with the point of your comment in general, and we shouldn't stop ourselves from creating something we value just because it exists already. Working on something we care about gives meaning to our life, and who knows, maybe your solution will turn out to be the best one out there.