Even if we go with your logic, what you described is HAMAS using Gazans as hostage - HAMAS threatening "the indiscriminate mass murder of Gazans through manmade famine" until the aid is given to and through HAMAS (and by using civilian population that way HAMAS does commit a crime against humanity). In such a case UNRWA at least should have publicly stated the issue and let the UN as a whole to decide. Quietly sending the aid to HAMAS makes UNRWA at minimum an accomplice. Financing a terrorist organization in response to its blackmail is pretty much a crime almost everywhere. And given the number of UNRWA employees being HAMAS members, some even openly participated in Oct 7 attack, it is definitely more than just an accomplice.

>UNRWA sustains life in Gaza.

and that doesn't seem true to me. Looking at pre-war Gaza - it seems that the regular Gazans have existed on their own, not much affected by UNRWA. There were businesses, trade, construction, some worked in Israel. Look at pre-war satellite photos - how much solar panels were on roofs there. I remember some Gazans even started to appear here on HN. And there was HAMAS fed by UNRWA. Removing HAMAS from the equation, there pretty much wouldn't be a need for UNRWA.