Channels that get big for the sake of having amazing quality tend to pick up production quality at some point, probably by hiring people. So if you're watching older/larger channels, the correlation won't be as obvious. On the other hand, we can time warp! This is the oldest video on YouTube from Veritasium: https://www.youtube.com/watch?v=cU2dZz18P0c

I'm sure there were plenty of even gankier ones prior since by that time he already had his nice logo sorted out, a pretty good broadcasting setup, and more. In any case, here's his latest video: https://www.youtube.com/watch?v=Q1bSDnuIPbo