Basically list building has been removed form the game as a tactical element. You have to get together with your opponent to come up with what the two of you mutually consider to be fair sides (if 'fair' is what you're going for, I've seen at least one battle report representing a deliberately lopsided game from MC1 - handful of skaven gutter runners and assassins trying to take out a wight king leading a larger undead host), and if you cannot agree then you don't have a game. If you play the game and decide that your chosen sides weren't fair after all, then you adjust next time. And if you are aiming for fair, then you need to take summoning into account when deciding on those sides.
But in general, yeah, trying to 'build a better list' in order to get a leg up on the opponent is just not a thing in AoS. There is no system mastery there because there is no system to master. There are tactics and strategy, they're just all during gameplay and not before it.
If you liked tinkering with lists and (especially) character builds, as I did, then it definitely feels like something's missing, but that's the long and the short of it. You have to come to the table trying to bring an army that will be as close a match to your opponent as you can, and then try to beat them with better play and better die rolling. If either side is trying to win by fielding a stronger army then the game will fall apart before it even starts.
The thing is, I don't think that jockeying can be entirely weeded out, and without any foundation to build on, I worry about arms races even among players trying to keep things even. We'll see.