Hamas has consistently stolen aid meant for civilians:

https://www.timesofisrael.com/gaza-aid-trucks-stolen-by-gunmen-and-looted-as-convoys-start-crossing-from-israel/

Before you scoff at the source, there's video evidence included in the article that is impossible to deny.

It should be pretty obvious that food, medical supplies and fuel are needed by fighters as well and in much larger quantities per person.

This is a difficult problem to solve. Personally, I would still send supplies though, hoping that at least some of them reach civilians who need them, but I can understand the frustration of people who are personally affected by this war. This aid unfortunately does have a not just theoretical chance of prolonging the conflict, enabling the besieged terrorist organization to hold out for longer, which in turn means more suffering not just for hostages and Israelis who only just recently have seen a reduction in rocket attacks, but also for Palestinian civilians, who are caught between a rock (IDF) and a hard place (Hamas) for as long as the fighting continues.

Here's the moral conundrum: Let's say we could determine with near certainty that halting aid would shorten the war, even if it resulted in a temporary increase in human suffering due to increased shortages. If the total amount of human suffering would be lower as a result, due to the war being over sooner, would it be the right moral choice, even if people end up suffering more for a brief amount of time? Think of it as a variation of the trolley problem.