These things haven't change in over 2,000 years. Whatever they're using here, it appears to have hit the bottom of physics.
That is quite interesting, isn't it? I suppose that there's a "bottom" to every technology. A point at which there isn't any further need for improvement or change.
Take for instance, the simple bowl. That's a design that's difficult to improve on, nor is there any practical reason to. A brick is a brick is a brick, unless it's a block, which is simply a variation on that timeless building unit. I suppose we could name thousands of human inventions that have hit their developmental "bottom".
Your observation would tend to argue that at least some of our visitors have reached a plateau in their technological advancement. It would seem to me, in that case, that scientific curiosity would have to be their chief interest in us.
There's also the political to be considered. Perhaps the Sol system is disputed territory. Perhaps it's even traded hands a few times.
Wouldn't it be interesting to find that our politics are little more than primitive tribal disputes, and that the politics that really matters is going on light years away from here.
Well, similar over 2000 years, but maybe not their 2000 years. Perhaps they are time travelers from our future and we see the same craft over time which it jumps around in, and avoiding contact because of the time paradox of changing the past. Or maybe they ARE changing their past to avoid what happened in our future, which given the subject of nuclear weapons, is rather dramatic. Who wouldn’t argue for killing Hitler before he came to power?