Without points your army is based upon what your opponent decides is fair, that new £50 model nope you can't use that.
My question how do you have fun building an AoS army when you don't get to decide what you play as you have to ask your opponent first?
As Ambrose says, this isn't actually the case. Because AoS is such a minimal ruleset, people are scrambling all over each other to try to make it "fit for purpose" and one of the first things that's come out of that is trying to impose army composition limits, whether that be numerically (number of warscrolls/wounds) or by agreement with opponent. But the rules have been out for less than a week and while there are obvious holes in them nobody is quite sure how things are going to shake out. Some of the solutions people are coming up with might well be for problems that turn out not to exist. In fact this is something which both amuses and concerns me: that the community is going to break AoS while trying to fix it because they don't understand what it is. I don't like the look of the game myself so it doesn't really bother me but I don't feel like it's getting a chance to breathe before being stifled by the sort of considerations it's almost explicitly trying to avoid.
Anyway. No aspect of army selection or deployment in AoS requires your opponent to approve your choices. If you possess the model and have a warscroll for it (and pretty much all 8th edition units and monsters have freely available warscrolls) you can use it. Your opponent may not like it, might forfeit, refuse to play you again, flip the table, drop-kick your figure across the room... but he could do that under the previous ruleset too.
That still may not help that much in collecting an army, as the variety of choice available might lead to paralysis, or the optimum game configurations being difficult to justify in the fluff. But the anything-goes approach also opens up some genuine possibilities that weren't there in the RAW previously (or at least before End Times): a Sylvanian army featuring both the Undead and living state troops, for instance; Ogres and Dwarfs back in an Empire army; a Marienburg army with substantial High/Sea Elven contingent; a Dogs of War army chosen piecemeal from every list! With some imagination it should be possible to come up with some really characterful armies. Whether with the destruction of the Old World and the likely discontinuing of the model ranges that'll be something desirable or easy to manage is a different question, of course.