To me, meaningful would mean something like helping the poor or working for a decent non-profit.
On the other hand, working for an ad-tech company and increasing revenue by 40% through some machine learning would have impact (on the company, clients, users, etc.) but not be particularly meaningful.
I don't see "meaningful" as referring to something like helping the poor, I see it as referring to feeling fulfilled. If that involves helping the poor, more power to you. Me, I took a $20k paycut to switch from writing node js all day to pen testing at another firm and I could not be happier. It's been two years since switching and I still look forward to waking up and going to work each day instead of groaning and dying a little on the inside. Paying $20k/year to be happy and feel fulfilled is a complete steal in my book.
Beware the seduction of perceived martyrdom. Are you really helping people, just making yourself feel good, or are you doing what you think other people will perceive as selfless? And yes, there's overlap between them all.
Ad tech is a second order business. You're helping other businesses fulfill their purpose. I don't blame you for not finding a connection to value there, but that doesn't mean you can't find one in traditional industry.
It feels like you’re talking about fulfilment, at which point we’re not really talking about the work itself, but the stuff that gets you out of bed in the morning.
