Have they?
I don't even think that's knowable in the present. That's one for future historians to decide when they write the history books I'm afraid.
Besides, not all growth is about expansion of the number of teams in the competition, and there's still plenty of potential opportunities for the AFL to grow if they're smart about it. I wouldn't be surprised to see them attempt a second division in the future either, though that'd still be decades away at the earliest I imagine, if it happens at all.
There's really not as far as I can see.
They rushed expansion and unnecessarily set the new side up for a rocky start, which is never a good thing. They've ignored major metros to focus on niche suburban markets again, a mistake that RL seems incapable of learning. Made further expansion in Brisbane a necessity when it could have been a luxury, and which will inevitably eat up valuable resources unnecessarily given time. They even allowed a broadcaster, and vested interest, to dictate their expansion decisions, and I frankly see no reason to be confident that they won't balls up the 18th team as badly as well.
At the moment it's a coin flip that the Bears, or maybe even PNG, end up with a license, and after that it'll almost certainly be at least a decade roughly, possibly longer, before they expand again.
We could be looking at it being the 2040s, maybe even 2050s, before there's a side in Adelaide again, and potentially Perth as well. That would be leaving at least one, potentially two, of the top five major markets on the table for at least a couple decades further, when it's more likely than not that it'll only become more difficult and expensive to expand into them in the future.
All that only addresses the professional tier, and largely ignores international markets, namely NZ, and all of it's extremely hard to justify. So yeah, I'm not seeing very many good signs, only the same worn out old ideas wrapped in a different colour wrapping paper.
Sure they could turn it around, strong leadership could turn it around overnight if they wanted, but I don't know that that's really that likely given the NRL, and it's predecessors, track record. . . I guess you reap what you sow.