Interacting with complex systems produces complex side-effects.

And ecosystem is complex enough that we can't really predict those side-effects before they happen and they can make other things worse.

Just spraying random stuff that happens to work on paper is equivalent in subtlety to electroshocking patient to fix their mental issues.

That is not to say it is not possible, but on top of being expensive it would require a lot of care to not make stuff get worse in other ways.