aliens feel very primitive and bruteforce right now.

They evolve not smarter, but more brute.

I want when you start the game, the aliens are just very basic, maybe a queen and some spawners, as evolution raises they start to get smarter and build more.

as it raises you get foot soldiers and builders, where one does raids and the other builds defense stuff, raise it further and you get a chain of command and more complex buildings, like a commander who groups foot soldiers and send several on scout missions to search for less protected areas and then invade them with force

By max level evolution, instead of only a behemoth here and there, you get this army of big mean guys lead by a behemoth with reinforcements coming from a big range of nests and attacking in a very strategic fashion, kill the commander and the reinforcements stop, but the bitters go wild and attack everything in their way.

Try to invade their base and you cant simple run over and turret creep, they have defenses against it, and a commander might order them to ignore turrets / bots and go for the player or call reinforcements from other nests, almost forcing you to nuke the bastards