I've thought about this for most of the day, and I have a theory, but I'm not going to say that I'm committed it to it at this point, but I still thought I would share it to see if anyone can knock it down or make it better:
I think there are generally two golf swings in golf: a swing for distance, and a swing for a target. That's certainly a messy statement.
A par 3 you're usually playing to a small-ish target.
A par 4 usually gives you one swing for distance, and one swing for a small target.
A par 5 usually gives you two swings for distance, and one swing for a small target, so it can feel lopsided toward distance, which is also why there are exceedingly few par 6 holes.
Anyway, that's the thesis, it's messy, and hard to defend, but i'll say this. I feel like if this thesis is right, there is a lot of room for long par 3s that have huge greens (probably prohibitively expensive to maintain), and short par 5s that require two very targeted shots (these do exist).
Those are my thoughts. I'm very intrigued by the proposition, mainly because I really agree with it without really knowing how to justify that agreement... even if my favorite golf hole is a par 5.