Finance and investment banking is about resource allocation. To get the stuff like agriculture innovation etc done, you need money. You need someone to look and say, this is worth investing money in. This is far from trivial. The investment firms try to predict what technology or company is going to make something profitable. This allocation task is very important. There are many ways to fail at producing anything useful. Intent purity is not sufficient.

Of course the suspicion towards this is eternal. People always hated the traders as opposed to the farmers. But trade is crucial. And it relies on estimating what value things have and rewards correcting over the incorrect beliefs of uninformed people. This kind of information based knowledge work was always disliked by most people as it seems lazy. And for sure there are zero sum and rent seeking aspects or insider trading etc. But it's not so simple as to say that all investment and finance jobs are negative and working on farm efficiency is always better.