I don't doubt that's the consensus opinion. However, the argument that Israeli settlements are somehow illegal nonetheless fails on numerous levels.
For example, you already understand that under international law the Jews were explicitly encouraged to re-settle in Palestine, as Palestine was declared the Jewish National Home. Article 80 of the U.N. Charter implicitly recognized the Mandate for Palestine (along with other mandates) and by Article 77 of the U.N. Charter the parts of the Mandate not incorporated into Israel fall under the Trusteeship system. Article 83 says the Security Council itself is subject to these provisions. Therefore General Assembly or Security Council Resolutions declaring Jewish settlements in Palestine "illegal" themselves have no legal validity.
By Article 79 alterations to the the terms of the Mandate must be agreed upon by the states directly concerned: in this case, the United Nations (since the Brits gave up their role as trustee) and Israel itself (since the Mandate was set up to achieve Jewish self-rule and Israel recognized as a sovereign state, whereas Arabs were denied political rights to self-determination in Palestine, having been granted these in Lebanon, Egypt, Iraq, and especially Transjordan (which comprised 70% of the original League of Nations Mandate territory.) )
Many of these terms are not unique as they were also applied to other de-imperialization reorganizations after WWI, when the Ottoman, Austro-Hungarian, and Russian Empires were broken up into separate nation-states.
Probably the most constructive thing the U.N. can do right now to support its stated purpose "to save succeeding generations from the scourge of war" is to reverse all their resolutions condemning Israel; it would certainly leave people like yourself less confused and angry.
