First of all every PhD I've talked to, at least in science, has talked about the incredibly abusive environment. Examples where their advisor ignores them and so they spend years without even getting a paper published. You can go on youtube and watch endless videos about the cruelty one has to endure.
Next I talked with a professor in engineering and even twenty years ago he said all his PhD student were foreign because it made no financial sense to get a PhD for a US citizen.
Then of course in even the least competitive majors there are 20+ candidates for each position and in the more competitive majors, it's hundreds or thousands of candidates per position. Most people trying to stay in academia end up in low paying, poor if any benefits and no stability post doc or adjunct positions.
Transparency and common sense in action:
1. Generally it makes no financial sense
2. It will mostly like be an abusive experience that will damage your mental health
3. There is so much competition that getting a good professor or research position is extremely unlikely.
The decline should surprise no one.