I wasn't making any equivalency, I just shared one specific example. There are obviously different degrees of errors, and the most benign errors may not be any worse than simply failing to record the out. (FYI, I edited my post above to show the error breakdown of UZR at Fangraphs, if you are interested.)
Errors are judged by the official scorer, which is an entirely different system than DRS/UZR/Statcast judging probability of outs. Not sure anything is wrong with that, but they tell us different things and they may not always line up.
If the superhero fielder drops everything, obviously he's worthless. But what about a superhero fielder who only drops a few more than the average player? Then the superhero may have, say, 5 more errors by the official scorer, but you wouldn't replace him based on that if he was responsible for a net reduction in baserunners/advancement compared to the average fielder.
In reality, with non-superhero players, these seem like marginal concerns compared to offensive outcomes. But when 90% of plays are routine like you say, the marginal concerns around the remaining 10% are magnified. And it takes a lot longer to amass a meaningful sample from those 10% of plays too.