Because his routes were always rounded off, making it easy for a decent DB to jump the route. So either he wasn't working on it, or he's not very bright.
A good throw can beat tight coverage. Troy Aikman said that. Romo to Dez didn't need any work. The connection between those two was excellent. Dez route running became a thing when the Dak friendly offense was established. That's something that people often forget. So if you look at the Dak friendly offense... it was china routes, dig routes, stick routes, quick outs, and comebacks. All short routes that CB's can sit on. The only person that could get open, running those routes, on a regular basis was Beasley. But people look at Dez like he could have worked harder. When it was the Dak friendly offense that tore things apart.
But my earlier post was about the coaches, basically. If Dez couldn't run routes then what the hell were the coaches doing? What were they doing in camp? It's not like they weren't trying, it's just that those shorter routes are timing routes. The QB and the WR have to work on those to get their timing right.
