That's a weirdly reductive and frankly useless way to frame the situation.

First, a paid firefighter and paid social worker are making the world better, just as much as a volunteer firefighter and charity worker. I'm not sure why you made the distinction.

Second, it's not a dichotomy between making the world better and worse. There are things that obviously are bad, and there are things that obviously are good. But there are also things that are almost entirely neutral, or somewhere in between. It's not an all-or-nothing situation: things can be degrees of good and bad.

If you insist on making it relative: these people are currently doing something more bad than what they were doing before. Whether you think what they were doing before was good or bad doesn't really matter. What matters is that this new thing is bad. And that's the problem.

I find the defense of someone doing active harm under the guise of "their job" to be shameful.