What, exactly, are we pinning on the "travel hacker" crowd here? AFAIK, the only Platinum card without a 1st year AF is the Ameriprise variant, and there can't be that many people gaming it and crowding the lounges. Everyone else is paying their $550 a year, so I really don't see what they're doing differently than you or anyone else. The root cause here is pretty simple - at airports where a Centurion lounge exists (at least at domestic airports), it is by far the best lounge at that airport other than the occasional international- or transcon-only premium class lounge. More context -

MIA - Maybe the AA Flagship lounge gives it a run?
SEA - No contest
SFO - UA (polaris only), VX, CX (only around the times of their own flights), EK are better
PHL - No contest
LGA - No contest
LAS - No contest
IAH - BA F, UA Polaris are better
DFW - Intl F (AA, LH, QF, etc) are better

I'm sure there are some omissions in that list - I googled, and made some guesses on lounges I hadn't been in, but tried to err on the side of caution.

Point is, of the better options, none of them are accessible for a $550 AF - and that fee bundles other benefits as well. The lounges are crowded because it's the best domestic product on the market and Amex hasn't built the capacity to meet demand at the $550 price point. It's not the consumer's fault. Any consumer. Not even Amex's - you can only build so fast. Their only real levers are to increase the price or restrict access, and they're apparently trying the latter now.