This!!
- At every company and institution I've worked for, I've never really been in a situation where two people, even if they have the same job title, are line-replacable for one another (unless they are very junior). Everyone has extremely distinct skills, experiences, capabilities whose value is extremely contingent on the needs of the moment.
- Making rules to make things for fair or transparent has the opposite effect. A major institution I worked for came up with an impossible-to-game, no-human-in-the-loop formula for bias-free and discrimination-free compensation. The result? People with equal responsibilities ended up getting paid _vastly_ different amounts. Similarly, people with equal salaries had vastly different levels of responsibility. I don't think a uniform compensation scheme simply works, other than just negotiating 1-on-1 with staff until agreements are reached, and when it no longer works out they ask Mr. Market.
- A company not disclosing salary already gives you enough information. Unless they are a flagship megacorp with well known salary bands and staff levels, and they are not disclosing the salary, then you know it's not competitive salary.