I dont know if there is anything necessarily wrong with your pitch. These days however, getting on one of these huge sites is HARD, so hard that its not worth your time.(I mean if you get covered great, bonus, but I wouldn't worry about it)

My suggestion is that if you want to get your startup talked about is to not focus on these generalist first tier blogs. You want to focus on the second tier. So basically find blogs that are interested in your startups space and have a fairly large following an pitch to them. They don't have people beating down their door to pitch to them like these other large sites.

The upside of these smaller second tier blogs is that their readers are generally passionate about their bloggers. Generally the readers of these blogs feel a connection to the bloggers they are reading(as they are individuals, not companies) and when they say they think a product is great, or interesting, or that their readers should check it out, the readers do.

These bloggers generally do around 3-5 posts per week, so you also don't have to worry about the post about your product getting lost in the mix.