Jobs are either deemed useful to increasing revenue by the business owner, or are deemed necessary by the government in the name of safety, fairness, accountability or just vote getting but which don’t necessarily add to revenue in the business. Which ones are meeningless ?
The economy is (or used to be) built on creating value and then exchanging it. So any job that doesn't end up creating value for a person somewhere (as opposed to a "system") is meaningless.
I.e. is the total value of the world higher when you finish your work, or is it not? If I am putting parts together to make a car, yes, the car is worth more than the parts. If I am suing someone by abusing copyright law, then no, I didn't add any value to the world.
There are certainly higher levels of meaning than monetary value. The issue the OP is raising is that many jobs don't even hit that lower bar.
From the perspective of 'creating something people want', a car does belong in that category, and a lawyer doesn't, but there will for sure be some grey areas.
Not all lawyers are bad. I've seen good ones doing good things in courts and telling people frankly what it will cost and what the chances are. And this one particular lawyer cost only 0.2X of his stated first round cost, because other side resigned after first letter. Now there won't be smelly/noisy food factory just right outside my apartment building windows.
What I'm getting at:
> I.e. is the total value of the world higher when you finish your work, or is it not?
TOTAL level of value in world is only correlated with meaning of job. But, there are many jobs which feel meaningful, but have negative effect on world.
Nothing to do with being good or bad. The work they do doesn't add value. It might even be necessary work so that markets can function, but it doesn't add value.