I wanted to be a police officer- not a beat bobby, but mounted. I was put off by my mum with similar arguments to your ex, no career, pay’s rubbish, you could go to uni and do so much better...
FFwd 30 years and I have a secretarial job where we work with the police a lot. The force now is huge- you can specialise in anything from firearms to countryside to terrorism, dogs, safeguarding, CID, forensics.
If you want the money and career there is a ladder to climb promotion wise.
Pay is above average, especially when you factor in overtime. Job is varied, and people move sideways between depts a lot to get a feel for where they’d like to specialise.
Those my age are now retiring at 50 with a hefty pension. Yes the pensions aren’t as great now, and you have to work a little longer, but still not bad.
If he doesn’t like it ex-bobbies are in demand elsewhere too.
It is definitely a calling, and it has it’s issues, but if he wants to do it I wouldn't discourage.
Especially now as they’ll fund you through a degree first.