Get better at words. The internet is largely driven by the written word, from social to ads to the sales copy on your website, being good at conveying yourself in writing is important.

I'd really recommend working on your skills or finding someone (either on a permanent or freelance basis) who can bring written skills to the table.

Forget YC, you can't expect your customers to watch your intro video or to test out your product if your written text doesn't convey the value it will deliver.