What do I do about my website's flop?

[Will]

Hi,

My website was once the 3rd popular one in my niche; getting 10-25 thousand hits per day. It was 3rd for my target keyword and getting over 100-500 hits from people searching that keyword per day. Then the site went down to 4th place and I was getting 50-70 hits from the keyword and 8-10 thousand hits per day. Then it went down to 5th place and I was getting 30-40 hits from the keyword and 5-8 thousand hits per day. Then it went down to 8th place and I was getting 10-30 hits from the keyword and 3-5 thousand hits per day. Now, the site is in 16th place and I'm getting 0 hits from the keyword and 1-2 thousand hits per day. What do I do?
It's now not much more popular than it was 2 years ago
@???
WordPress.org. Sadly, my site is hosted on WordPress.com.

[???]

Why? Look at the other sites which are now beating yours. What have they got that you haven't?