It also shows how people's eye tests really suck at evaluating defense over a long season. Mistakes always get remembered vividly, the dives and "spectacular" plays get remembered, but those make up like 10% of a season. The plays they make routinely that aren't routine but only look slightly difficult are very much as you say, taken for granted.
The second part is when you watch a team for 162 games, there's a tendency to be much harder on them or have a "this has to be the worst ..." because you'll see a guy make 3 mistakes in a week and remember that for the rest of the season because you see that guy every day... and your brain keeps assigning those mistakes to him over and over again even though they don't get repeated.