It's not even that he didn't try, although that's a valid point, it's the fact that he doesn't have any sort of message discipline.
The campaign of course is producing ads, and they have generally been hitting Kamala on the areas that you would expect them to (ie. immigration, economy, etc). But when he has had public appearances, such as the Atlanta rally over the weekend, he not only didn't focus on or reinforce any of those issues but actively made life harder by, for instance, going after the wife of Governor Brian Kemp. To be clear, he wasn't clear and concise and rambled a lot in 2016 as well, but the degree to which he is consumed by grievance and articulate any sort of substantive message is markedly different when you compare to videos of him from that campaign.