How strange- most of the people I see up there are significantly senior to Gen Z.
You seem pretty angry about this, but honestly it’s pretty fair in my experience. Paying customers get first pick of the first/business/econ+ seats. If the higher fare cabin doesn’t sell out, the customers who have purchased a seat and have the highest status with the airline get the next chance at upgrading.
Because I can easily spend $20-30K per year on tickets (for my employer mostly) I have high status on UA, but I honestly don’t get upgraded very often. It’s fine- for domestic travel, the ability to select economy plus seats or exit row without a upcharge (and free check bags) is of greater benefit to me, and those rows often have open seats in them anyway. For international travel, it’s miles, business travel policy, or suck it up in coach.