I wanted to get a PhD in CS at 40 but was convinced by a local professor of CS that it was a waste of everyone's time and there were no jobs to be had in the academic world anyway. Shortly thereafter Google started hiring them by the truckload. I wish I had ignored him.
I did have a 4 decade career as a programmer, but who knows what might have happened if I had taken the time mid-career to do the doctorate.
Ironically, CS professors and teachers are, from last I heard, in extremely high demand now because so many CS PhD grads leave for industry (and 3 or 5x the pay of academics). I don't think that was just as adjuncts either. Some universities are willing to pay way more than adjunct salaries to get CS grads with real teaching ability. I doubt you'll ever see industry competitive salaries though.
This economic opportunity is only true for PhDs in CS or engineering and even there, only for hot research areas. Good luck getting 5x academic pay with a PhD in geology.
Generally speaking, the professor's advice from 25 years ago is still solid: don't get a PhD unless you are interested in an academic career, research, teaching etc. Due to the prestige of such a career, it tends to have an oversupply of applicants - the majority of which will not get a commensurate payback for the efforts required by a proper PhD thesis. So they will either flunk / present a low effort thesis, or worse still, they will invest a few years into a good thesis but never develop their career and skills gained into a full academic job.
So getting a PhD for the sake of it might not be a good investment of your time and effort career-wise; If you want to do it for the intelectual challenge on a topic you are very interested in, that's always a suficient motivation.
I did have a 4 decade career as a programmer, but who knows what might have happened if I had taken the time mid-career to do the doctorate.