I fully agree: even the game is open world, it definitely should scale with the player’s team strength and time. You shouldn’t have to deal with enemies you have no chance of beating early in the game.
Imho, the developers of the game should try to make the game fun for everyone, not just those who feel that the game should be as difficult as possible. Maybe, there could a setting which would decide how long does it take before high level enemies start appearing and how fast their population increases.
I think at this point the game can be much more frustrating than enjoyable at least early in the game where one wrong chose or just some bad RNG can easily get your whole squad killed.