He did overestimate his abilities though. Maybe not today, but he did at one point. You don't get a mess like "The Wall" without an idiot thinking that what he was doing was far greater than it actual was. It wasn't bad for him to try new things, but all the things he did were repeatedly crap. Everyone told him that they thought Demo Reel was crap, so he goes back to doing Nostalgia Critic. However, he tried for years to make it be like Demo Reel despite fans telling him that that wasn't what they wanted in Nostalgia Critic.
Regardless of what stories from behind the scenes that have been spun about Doug are true or not, it is obvious that Doug did want something more out of his career and thought he was going to get there with the things he did. There were a lot of points far earlier where he should have realized things weren't working. He also should have realized much earlier that he was out of his depth with managing the company. We also have everything that happened with the Indiegogo campaign.
The thing with Doug though is that he did realize eventually that the things he was doing weren't productive and he should be doing what the fans actually wanted out of him. He realized what his abilities actually were and what people liked about him. He is arguably one of the only YouTubers who found comfort with his craft and realized what there lot is in life.