It's a team based game, for the most part. You have to pull your own weight; it's okay to slip up sometimes. Harassing someone is a no-go. It only toughens up both fronts.

The problem is mindsets between players. FFXIV doesn't require you to play moderately well outside of Savage, so it's easy to see why some people don't put any effort in. Raise the difficulty and you have another problem with people saying it might be too difficult. You can blame SE in this aspect for trying to bring people together in content that requires coordination. The trust system is the right step. They only need to expand on it.

As for toxicity, you have no idea what's going on in Discord servers. People might be friendly in-game but they definitely aren't in VC. The ToS does a good job of creating that illusion but ultimately reality looks vastly different.