Oh dear. Do away with the em dash? Putting my personal affection for the mark aside, I’m hesitant to sub one form of punctuation for another. After all, you wouldn’t just swap out commas for colons. Although the em and en are both dashes, they have different meanings.
The en is primarily used in place of “to” (the 2010–2011 school year), but the lovely em dash—which The Chicago Manual of Style describes as “the most commonly used and most versatile of the dashes”—has many functions. It’s most often used to set off explanatory information, as in the previous sentence, or to indicate a break in thought.
To let you know where I’m coming from, here’s what Chicago has to say about dashes: “Hyphens and the various dashes all have their specific appearance and uses. The hyphen, the en dash, and the em dash are the most commonly used and must be typeset correctly; an en dash appearing where a hyphen is called for bespeaks editorial or typographic confusion.”
I assume they would apply the same logic to replacing an em dash with an en dash. Since it seems it’s the length of the em dash you object to, I suppose shortening it—while retaining its meaning—is a good compromise (but you should know there are 2-em and 3-em dashes). Visually, I like the way the em dash looks because it illustrates the separation that’s intended.
When it comes to punctuation, I’m more concerned about function than form, which is probably the opposite of how you feel. But I’m sure we have the same end goal in mind: readability. Maybe it would help if designers read The Elements of Style and editors read The Elements of Typographic Style?