That is a solution, there are multiple other solutions all equally or more likely that don’t involve murderous aliens.

One just as out there would be a sort of galactic zoo - there is simply an agreement not to interact with intelligent life before they reach a certain step, say establish global unity or develop a certain tech.

It could be that we are in fact a statistical outlier or are simply wrong in our probability calculations.

It could be that intelligence develops but spacefaring is rare. It could be that intelligent life simply has a tendency to collapse before it gets there. It is certainly still possible for us and it is not like we are making super meaningful progress towards space colonisation.

It could be that there are not great viable interstellar travel options, almost every option we have thought of that makes sense time wise has big ifs attached to it assuming we have a good idea of physics. Of those probably relativistic travel is the most likely and even then it would take quite a decent chunk of time to span the galaxy, going to war on those timescales is basically non-sensical.

I expect that any civilisation capable of cooperating at scale to achieve meaningful interstellar travel would also be developed enough in ethics to most likely not pose a danger to us.

A civilisation capable of waging war like that is probably around a K2 civ and the idea that a single planet somehow threatens them is also silly. Even a fully K1 civ to them would be close to a stadium packed full on earth in terms of relative size.