Neville, it’s important to understand that without daf yomi, many people wouldn’t learn at all. Roshei yeshiva aren’t going to blast something which is flawed but gets people to learn, because it’s not as if they’re going to drop it and leatn sugyos biyun slowly, covering maybe an amud a week due to their work schedules.
Also, a large amount of baalei batim simply lack the ability to learn sugyos biyun. Many can and do, as kolel yungeleit transition to the working world.