Don't think raids or rewards are a problem. Blizz has been downplaying the idea of guilds and groups for years now, and that is the main issue. The social aspect is gone and players are conditioned to instant grouping with people they will never meet again, so joining a guild and working around a shared schedule is just alien to many people at this point.
And M+ did not help, as it's a lot less work and time investment to get a group and do a dungeon, and there are no lockouts, so you can do it whenever and with anyone. Also you are pretty much guaranteed loot that is as good if not better.
So raiding became more of a high investment and uncertain return option with a bunch of restrictions and inconveniences.
I think what we need is a revamp of the guild system. And in needs to address several points:
- There should be a a barrier to creating a guild. At this point it's really just a matter of signatures, but it should be more involved. And not just a high price to create one, it has to involve effort. For example you can start a guild, but you need to do a bunch of quests and tasks together to get it "official", like setting up your base and getting the infrastructure in place. So that people are invested. And it should not be just some material donations or some shit, that could be done by one person with enough gold and willingness to visit AH.
- There needs to be a reason to join a guild, a tangible advantage. Yeah, we have perks, but they were nerfed so many times they are pretty meaningless for the most part. In BDO guilds make a lot of money on daily basis but also give a lot of it back to the members in wages and salaries (one is daily the other is based on your contribution to guild quests).
- We also need a proper way to recruit members and find guilds, that does not involve shouting in trade chat. I once tried to find my guild using the in-game tool on a new char, I gave up after about hour and a half of scrolling.
- There should be guild activities and a reason for both guild and it's members to care about them. Tangible rewards and need for cooperation, not just world quests and do X dungeons in a guild group.
- Guilds need bigger presence in the world, more than just <Taste good in your mouth> under your name.
- There should be things for GM and officers to do that affect the guild, and a reason to have officers and specific jobs for them, beyond "you can recruit and kick people".
Basically guild system needs to be a proper part of the game, not a tacked on system that's been mostly left alone for 15 years. You get people together and invested in what they are doing and who are they doing it with, they will naturally gravitate to activities they can do together. Not the other way around.