There are two main schools of academic thought today when it comes national and ethnic identities. The modernist one, which is currently very popular in academia, argues since no one is pure anything ergo identities are purely social constructions. Someone is xyz because of conditioning growing up and the choice to define themselves that way. There is certainly some truth to the argument but this worldview also ideologically sidesteps the issue that self-defined nations and ethnic groups do in fact exist. IMO the mistake modernists make (typically leftists trying to show their peers how they are antinationalists) is thinking because we never step into the same river twice this means there is no river.
The secondary types (which I subscribe to) is primordialism. This school argues although purity is a myth, there is a flow to history and recurring key themes like aspects of education, or territorial association, or language, or religion, or laws, or customs, and so on. This is exactly why even though Americans is not an ethnic group we can still identity George Washington as an American historical figure not a Cuban one. In this view some modern identities are purely modern constructions and others have an ancient past due to the aforementioned recurring cultural themes..
In the case of Jews.. its their religion. And they did in fact care enough about ancient Israel to resurrect the Hebrew language. In the case of Palestinians… there is no cultural connection to ancient peoples that lived in the region. There is not even an attempt to speak the language of ancient people. Or the religion. Or the customs. Or anything else. The main argument is genetic link but a few genes in common alone isn’t enough to argue a primordialist origin since everyone has mixed. Palestinian identity is purely a modern invention from even a primordialism view..
Primordialism is what most laymen think of history but my observation has been when someone is hostile to another group they flip-flop between primordialism histography standards for themselves, then change to modernist standards for those they are hostile towards. Many don’t bother to notice they have less in common with their claimed roots than those they criticize.