I'm willing to accept that spectrally-resolved IR imaging can detect people, and give some information about what they might be wearing or carrying, under some conditions. If you use longer wavelengths, things like curtains don't matter much. If you resolve spectrally, you can probably do it during daytime (non-spectrally-resolved VOx thermal imaging scopes generally cost a few thousand dollars and are approximately useless during the day).

But under what battlefield conditions? IR doesn't penetrate concrete. It's hard to get anything through concrete. The wavelengths that penetrate well enough to be useful at all have such low resolution that I seriously doubt that you can see a phone or even a gun given the acceptance angle of any reasonable detector. I don't think mud brick or sandstone is very good for thermal imaging either, and those are the main construction materials in Gaza.

So, physically, how does this work? Ask Hamas to come outside before attacking, so you can spare civilians?

Hamas could already release all the hostages and surrender, and that would spare all the civilians.

Also, how does this solve the "we don't want to get within firing range of that Hamas outpost until we've bombed it" problem? Aren't most of the deaths from bombing, and isn't most of the bombing done (nominally) to avoid excessive casualties among IDF soldiers?

Furthermore, even if this works under a large enough fraction of battlefield conditions to be widely deployed, is it widely deployed?

You seem to be criticizing Israel for not doing something which borders on fantasy at least for right now. I don't know of any army that has this deployed widely, and although Israel is known for world-leading military technology, before deciding that Israel likes killing Palestinian civilians is the reason, shouldn't you document very clearly that they actually have the capability at all levels (tech exists, is provisioned, works with logistics, etc.)?

I think it is extremely important to try to safeguard the lives of noncombatants to the extent possible. That "use thermal imaging so you can shoot at the men who probably have guns" is the answer seems very unlikely to me.