First, we have to get past the reality that no one can know your thoughts unless you express them.
Yet still it is only a thought, even if I write it down and hide it in my drawer and housekeeping finds it. So you have not yet wriggled out of this space of convicting only for for thought crime.
An apostate leaves Islam. Thats how their apostasy is "expressed": they stop believing Islam. Punishing that is convicting thought crime no matter if the apostate tells nobody explicitly or tells 100 people. So, even expressed in this way (letting everyone know), you STILL haven't wriggled out of the space of thought crime, try as you might.
By the way, that thought crime conviction seems to be very practical in some countries. They even write it down. And they punish people for it.
Your label of"impractical" is just a tactic to avoid admitting and making moral judgment, I think. I think we can create a very objective (not to say, all encompassing) standard of morality.
And yes, our culture/system/social contract, whatever, is superior to that. Objectively. Measurably.