I think it's more nuanced than just them trying to "prevent clean water and food and medicine from crossing the border." In the region, water is scarce and important for both sides. Israel does allow "clean water" into the region, the complaint is that Israel government allows their own people take too much of it (from the perspective of Palestinian farmers). In the American west we have the exact same problem. Farmers higher upstream of the Colorado river want enough water for all their crops, but this would deprive the farmers further west from having enough. There are intense and heated (political) battles between the regions, with both regions feeling like they are getting shortchanged. With food, medicine etc, there's concern that those supplies are going to enemy combatants/terrorists (from the Israeli perspective).
This is one of those situations where there aren't really any clear/easy answers.
(These are honest questions, from someone with essentially no understanding of the current conflict but is trying desperately to make sense of it and is struggling with obviously biased reporting everywhere I look)
Now, you need to divide your concept of thr Palestinian people to (at least) 2 groups or factions, those that live in Gaza and those that live in the west bank. The major difference between these groups is that Israel is the sovereign over the West Bank but disengaged from Gaza about 18 years ago and since it's disengagement, terrorist groups like Hamas have taken control of the Gaza strip[1]. One could have a long conversation about human rights issues in the West Bank but what is happening in Gaza right now isn't oppression, it's a war. You could point out Israel's blockade of Gaza as a form of oppression but it's just a way for Israel to prevent Hamas from accumulating massive amounts of weapons from certain foreign actors[2]. The really terrible thing ia that Hamas's infrastructure is so deeply linked and interleaved with civilian life it's impossible to fight them effectively without hurting civilians (Israel has some measures to attempt to do that[3] but everything has it's limits). Hamas isn't interested in peace and will slaighter their way to victory whatever happens, they are actively hurting both Gaza and Israeli civilians as we recently observed with the cruel massacre. The world will be better without Hamas, it's heartbreaking it has to happen this way.
[1] https://en.m.wikipedia.org/wiki/Israeli_disengagement_from_G... [2] https://en.m.wikipedia.org/wiki/Iran%E2%80%93Israel_proxy_co... [3] https://en.m.wikipedia.org/wiki/Roof_knocking
A good bit of it is quite simply explained by "they want to do a genocide and this is an effective way of doing it."
The blind blame of Israel is just tiring. They still want all the land and drive out the Jews. That is no basis to found a prosperous nation.