even if every other planet/galaxy did follow the same fundamental laws as our own, you can't really say that you could foresee what to expect there...
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If we discovered life on another planet even with the same fundamental laws, we still have zero idea what to expect...
Exactly. If the laws there are different, there is no way that we can really predict anything, but if they follow the ones we expect, we can say something. So as long as nothing happens that shows that ours are not working for that system we use the theories that we have, and expect. In fact, in our current system, Noether's theorem states that for each conserved quantity (eg momentum, mass-energy) there exists corresponding invariance (in this case invariance wrt translations/rotations, or time), so this should happen. And if the rules over there are that far apart, well we don't really care since having different laws means we can't say much about what is happening.
The problem with foreseeing how life would develop comes from the complexity of the beings in question. We don't understand why Earth developed why it did (as a whole, we have some underlying causes, but we can't say why exactly each trait was favoured at each point), so under slightly different circumstances wildly different results will occur (like in the 3 body problem), on the other hand for huge systems like galaxies each individual perturbation is so small compared to the whole that we expect the entire thing to still follow some pattern, a bit like with matter around us as opposed to the probabilistic world of atoms.