I have been in the same situation a few months ago and after much thinking and hand wringing, I decided to create the website but focus on markets in other languages.
Since then, from developing my idea for the japanese market I got a completely new idea that is easy to develop using the same code and for which there is currently no competition.
So, I think that you should try to develop your site and try to see if you can differentiate your site by either targeting another market (other countries) or create a spinoff for a different kind of field.
Comments
I have been in the same situation a few months ago and after much thinking and hand wringing, I decided to create the website but focus on markets in other languages.
Since then, from developing my idea for the japanese market I got a completely new idea that is easy to develop using the same code and for which there is currently no competition.
So, I think that you should try to develop your site and try to see if you can differentiate your site by either targeting another market (other countries) or create a spinoff for a different kind of field.