Obviously if your business strategy is "build X but better" where X is some incumbent on the market you already failed. Because they have everything that you as a start-upper don't have.. money, resources, visibility, name recognition etc. They can simply out compete you anywhere. And if the only value added and USP is "better" (even if that is objectively so by some metric) you really need to be 100x better in order to overcome the inertia that people have when switching over to your product. (Or you need to throw money at the problem...)
As a startup you really need a completely different USP and value proposition, look for something that that existing platforms/products don't do so well (or don't do at all) and see if there's a market in that particular niche.
Two sided markets (like LinkedIn) where you need both sellers and buyers (in this case employers and employees) are really hard because you have a chicken-egg problem and you can't get one side of the equation without the other side. So you really need to crack this by solving some other problem first that you can get either group on your platform before you can start dreaming of creating that kind of platform for sellers and buyers to meet.
As a startup you really need a completely different USP and value proposition, look for something that that existing platforms/products don't do so well (or don't do at all) and see if there's a market in that particular niche.
Two sided markets (like LinkedIn) where you need both sellers and buyers (in this case employers and employees) are really hard because you have a chicken-egg problem and you can't get one side of the equation without the other side. So you really need to crack this by solving some other problem first that you can get either group on your platform before you can start dreaming of creating that kind of platform for sellers and buyers to meet.