As you judge (say with bias and disregard for the truth), so will you be judged.
That’s what you need to understand.
See the part you put in parentheses? You added that. So now it says that if you judge someone without regard for the truth or if you are biased, you'll be judged, otherwise go ahead and judge as long as you know the truth first. What if the truth you think you know is tainted, altered, a lie and you misjudge?
Here is a truth stated several times in scripture: You
shall not add to the word that I command you, nor
take from it,.
Because in doing so, you can come to an erroneous meaning.
As far as knowing the truth, since God judges a man's heart for the truth, and we can't see a man's heart, the truth eludes us. That may be why God tells us not to judge. He said vengeance is His.
You didn't respond to the rest of the scripture that lays why not to do it right out there. It's that, never mind someone else's sins, sweep your own porch, part that tells us why we aren't qualified to do it.
Sometimes it just says what it means without any further metaphysical interpretation. Instead of trying to figure out who you are worthy to judge, and who you aren't, wouldn't it be more prudent just not to do it at all, and to accept the blessing of not being judged, if that's what that literally means?