There are many reasons why using Israel as a scapegoat is useful internationally and it is not contained to european countries with a history of the holocaust (putting aside Ireland's relations with the Nazis)

For a quick understanding of the situation it is easy to see international organizations like the UN human rights council which disproportionally condemn Israel while are free to elect a chair from countries like Iran, whose hobby of hanging gays from cranes is possibly one outlet of adherence to human rights. 174 condemnations for Israel this decade vs 10 for north korea, a country known to operate actual concentration camps

Generally this is a shift from scapegoating jews in national politics to scapegoating Israel in international one, or alternatively to scapegoat internal issues (see corruption cases in Spain, South Africa)

Regarding your opinions about Israel war being indiscriminate towards civilians, I mostly disagree, however this is not my point. My point is not the criticism of the effects of bombing in a dense urban zone (where civilian hostages were taken to, attacks came from, and popularly elected Hamas is entrenched in), but calling such attacks a genocide. These are so hyperbolic that another explanation must be found, and because we have a cultural history that is older than all nations of exactly such allegations, that is the most fitting explanation in my opinion