Every time I fly I see the same problem. Planes are boarded front-to-back. You always get a “traffic jam” of passengers stowing their gear and waiting for others to sit down and get out of the way.
If they boarded staring from the rear, this should be mitigated to a large extent.
This seems common sense. Why don’t they do it? There must be a reason.
They could board first and business class and then reverse board.