B) Apartheid South Africa used the same excuse. That black people lived in independent bantustans who were self governing and therefor not apart of South Africa.
C) You are ignoring the fact that Israel very much controls Gaza, including every border crossing, the airspace and sea access, imposes a blockade, controls the registry, etc. Unlike apartheid South Africa, Israel does not recognize independent Palestine, let alone independent Gaza.
B) The apartheid in South Africa was based on race. By contrast the different policies in the West Bank reflect the historical and cultural context there: that it used to be part of Jordan, that the people there want to be separate from Israel, etc.
C) Israel does not control Gaza's border crossing any more than the US controls Canada's border crossing. Israel is an independent, sovereign country, so of course they get to control who goes in from Gaza. The other border gaza has is with Egypt, and Egypt has the same policies.
Palestinians in the occupied territories may not be Israeli citizens, but neither were the South African residents of the bantustans, so which passports the subjects of Israel holds doesn’t matter. What matters is that Israel controls most aspect of their lives and imposes different rules and condition depending on whether you are Israeli or Palestinian. However you separate the population doesn’t matter either, the fact that Israel does is all that counts.
There is a different legal system on the West Bank, true, however the Israeli settlers living there get charged in Israeli courts, and so do Palestinians, except that Palestinians get charged in a different court system, namely military court. This is a double justice system, and there is no other way of describing it. Modern liberal democracies don’t have those, only apartheid states do.
Gaza was reliant on Israel for water because Hamas not only didn't invest in infrastructure, but literally dug up water pipes to make rockets. Why the heck should Israel be responsible for providing Gaza with water, food, fuel, or electricity? Do you also believe Ukraine should provide this stuff to Russia?