But what if the shoe *doesn't* fit?

There's a Hungarian saying, "akinek nem inge, ne vegye magára". A literal translation is "if it's not your shirt, don't put it on".

Practically every dictionary I checked equates it with the English saying "if the cap/shoe fits, wear it", but to me, the meanings are precise opposites: the Hungarian saying means "if you don't think the criticism applies to you, why the heck are you getting offended?", while the English expression is more like "if the description applies to you, then guess what: so does the criticism".

Is there a better English equivalent to this saying? Does anyone ever use "if the shoe doesn't fit, don't wear it", and would anyone know what it's supposed to mean?

Solution 1:

We do have this idiom:

like water off a duck's back

You say that criticism is like water off a duck's back or water off a duck's back to emphasize that it is not having any effect on the person being criticized.
_{Source: Collins COBUILD}

In Endangered Phrases: Intriguing Idioms Dangerously Close to Extinction, author Steven D. Price elaborates:

Duck's feather are waterproof. The preen (or, formally, the uropygial) gland at the base of the tail produces oil that spreads and covers the birds' outer coat so that water forms droplets on, but does not permeate, the feathers.

That's why a critical remark that doesn't bother the person for whom it was intended rolls off like water off a duck's back.
_{Source: Endangered Phrases}

For the sense of advice, it is combined with an imperative—something like:

Let it roll off you like water off a duck's back!

Yes, that's a little different than your Hungarian aphorism; it could just as well mean one should ignore the criticism even it is true. To get any closer, we'd be leaving aphorism land:

If the criticism doesn't apply, just let it roll off you like water off a duck's back.

_{Further reading: The Free Dictionary provides a roundup of usages from various sources.}