Agreed
Perfect Practice Makes Perfect
The only way to get better at sight reading is to constantly get **new** sheet music that you haven't seen and give it a try. You'll only know what it should sound like if you have somebody else's performance of the same piece to listen to. And of course different performances of the same music can sound vastly different.
Another note: Practice with other musicians. the challenge of keeping up with others can make you sight read better.
One