“Saying ‘it’s impossible to know what G-d wants’ is a cop out that just lets everyone do what THEY want.”
That doesn’t follow. Hashem gave us the Torah, but it is up to us to interpret it, and even the greatest gadol, by virtue of being human, will be unable to unlock every last secret of the Torah. It’s not that we can just throw up our hands and “do whatever we want”– we need to do our hishtadlus– but we should also recognize that we are in galus and we have no nevua, and so we really have no way of knowing how our actions are being received in shamayim. It’s a truly humbling thought.