I've been saying for a few years now, the NFL game is impossible to competently officiate now.
First of all, there are too many rules, and too many of them are interpretative, especially when it comes to blocking and tackling. Second, the game simply moves too fast and there is too much going on in short amounts of time.
People expect 50+ year old men to interpret these complicated rules in these short bursts of time, and do a competent job? I don't have the answer, because the player safety issues necessitate these new intricate rules, and players aren't going to get slower or weaker. But what I do know, is the game has evolved to the point that it's nearly impossible to officiate.