I don't think the NFL will expand again, at least not anytime soon. To many of the stadiums are normally at 50% or less of capacity. TV ratings are declining (slightly, but still declining). The Market is changing, and the revenue stream might not be able to grow as much in the future as it has in the past. There hasn't been any serious expansion talk in 30 years, and the current group of owners is unlikely to be willing to split the revenue with more teams. And if it does happen, its likely to be international. I think this would be a mistake, but almost all expansion talk centers around international expansion.
For Mingo to do his job, he has to get separation, correctly run his route and catch the ball when it's within his grasp.
For Young to do his job, he has to make pre-snap reads, get adequate pass protection, correctly identify the receiver, put the ball where the receiver can get it, and hope to God he gets it (unlikely if "THIELEN" is not on the back of his jersey).
So while there are mitigating circumstances for both, they're not an apples-to-apples comparison.