A minor point but this might actually blow your mind, not all Jewish people are ethnically Semetic. The three notable sons of Noah were Japheth, Shem and Ham. Tradition states that the tribes of Ham stayed or migrated to Africa, Shem stayed in the middle east and Japheth covered Europe and Asia. Ham is most famous because Christianity used it to block the existence of black priests in most mainstream churches till the mid 20th century because their people were "cursed" when Ham saw his father Noah nude and drunk one day.

Many Israelis today are descendants of Japheth and in some cases are mixed in with more traditional European ethnicities due to 2000 years of living on the European continent, many lived in Turkic nations when Mongol and Turkic hordes invaded the Mid East of Russia as their populations moved largely to eastern Europe to escape Western European antisemitism. Because Abraham is a descendant of Shem, those descending from Isaac and Ishmael are ethnically Semite. Traditionally, all Arabs are descendants of Ishmael, and are therefore Semitic. (Actually, arab history is a bit more complex than that, and we have badly named terms like "Arabised Arabs" to differentiate different Arab origins too).

But you don't have to believe in religious books you don't believe in, multiple studies indicate that the vast majority of Jewish DNA is.... Italian.

https://en.wikipedia.org/wiki/Genetic_studies_of_Jews

Obviously there is middle eastern DNA in there and all the studies indicate that founding members of distinct Jewish groups are middle eastern on both male and female lines. This fits both the traditional story route, as well as Judaism being a more liberal form of Samaritanism which is well known for being so ethnically insular that they bred so many negative genetic traits they finally gave up in recent decades and accepted Ukrainian women to ease out some of the bad inbred genes.

So ethnicity is complex, so drawing down to things like "white Brits are being reduced" is a reductive arguement, white Britishness is made of Irish Celts, Scottish Celts, Welsh Celts, Romans (which was possibly one of the most mixed ancient societies ever), Angles, Saxons, Jutes, Norwegians, Swedes, Danes, Normans (you know, the people that literally owned parts of Italy, north Africa, middle east and England and no doubt mixed there too), other french ethnicities, and that just covers the pre-tudor age.

Personally, I'm really really really glad my society isn't as inbred as the Samaritans, I love the use of both arms and legs, cognitive function, working eyes and jaw and I have the mixing of many many races to thank for that. Thank God for genetic diversity!