When your only reliable way to get a pay bump is switching jobs adopting any system that ties pay to tenure seems awfully synonymous with pulling up the ladder behind one's self.
Not sure where "tying pay to tenure" came up, unless that's how you view what unions do? A union just means a group of employees negotiating as a unit, what changes they ask for isn't dictated in advance.
Surely a next-gen labor union based in the tech industry could find a new way to fight ageism without mandating a seniority system. Why does tech have to act the same way as before? I thought we were supposed to be innovators?
When there is a proposal that is suggested, there are proponents and detractors. That is tautological. Blankly insisting that things are good enough is just as empty as blankly insisting that things aren't.