Personally I don't see any problem with AA's 1-9 zoned boarding SOP. It works well for me and the times I'm approaching the boarding area late (late connection for example) and they are on group 5 I simply walk up to the 1-4 lane and immediately get processed. That's the way it's supposed to work and I think AA does a good job at this.
What I don't like is what I CAN"T control and that's people who rather step into their row to put their bag in the bin do so from standing outside the row dead front of incoming passengers. Unless you are disabled or recently broke your arm there is no need to do this facing the bin out in the aisle. Also, don't get me started on the people that do this who also gracefully and slowly take off their jackets, pull out headphones, etc like they are Fred Rogers walking into their home in front of their own closest. Ugh...this isn't your living room people. Yes AA has made and does make announcements to these slo-pokes in a friendly PA announcement "good evening folks we cannot complete boarding process until all of your personal items are stowed and you are in your seats". If I had my way my PA would be a little different LOL