To succeed with Internet marketing you need to be able to communicate. And the way most of us communicate on the Internet is by writing. Being a good writer is necessary because you promote your product and get your point across by writing. You need to acknowledge, right at the beginning, whether or not you are a good writer. If not, there are several things you can do:
Take a class in writing skills
Hire others to write your copy
Use a video, instead of written copy, to get your point across
And just a note on the last item because, even if you use video, you still need to be able to communicate. You need good copy that you will speak on the video. And you need to be able to speak in a clear manner that won't cause your listeners to fall asleep.