Much of these problems could be easily mitigated by direct involvement from the gate agent to get the lines in order before boarding. At wide body gates, there are plenty of gate agents for one to step out and get the pre boarding lines setup in order and use the straps to minimize cutting and pushing into the line. Until everyone is in a single file line, no one should be boarding. At narrow body gates, proactive announcements can get all of the right people int the right lines well before boarding begins, and that includes making sure that the ONLY people standing anywhere near the gate are disabled, GS, 1K and families with strollers and children under 2 (this should really be defined as families with strollers or infant in arms only). If you're not pre-boarding, or in G1 or G2, you should be sitting down or standing far away from the door area.

The fact of the matter is the GAs, for the most part, just don't care - whoever shows up to wave a boarding pass under the scanner is let on, half the time they don't even look.

I'm particularly annoyed with the chaos of United boarding, and Air Canada boarding which is often worse than United with far more aggressive cutters and pushers because when I was a GA back in my college days, I ran my boarding with military precision, and that included paying attention to what was happening in front of me, and I would absolutely call out line cutters and pushers and have them step out and wait to board last in their priority group. I rarely had any of these problems because I wasn't afraid to get on the PA and be proactive so everyone knew how boarding would be handled.

At NRT, for the most part, they can board a widebody in half the time a US based GA can board a 737 because of going out into the line with signs, and sorting everyone into single file groups inside the straps which makes chaos and shoving much more difficult.