Get the right people in the room for the right reason. You will be much more likely to host a great event if you can check those two boxes.
Right people is hard because most events want as many people as possible. The marginal cost of another person is low and the marginal gain is usually high in comparison.
An example of the wrong people would be a networking event for everyone in the business community. It's easy to add another person at $15 a ticket. It's hard to make genuine connections in an open room of 200 people.
An example of the right people would be a wedding. It's fun to get extended family together for an exciting occasion. Having the right people there creates an environment where you feel welcome and able to enjoy the event.
Right reason is about the expectations that people have when attending an event.
An example of bad expectations would be not setting any expectations and hoping for the best. That's how most networking events happen. "Come hang out with other people interested in business."
An example of good expectations would be letting people know that they might have to get vulnerable, but if they follow through, it will be well worth it. Maybe it's a smaller workshop about personal development. Telling people ahead of time that they will have to have deep conversations will better prepare them for a successful event.
If you can get the right people to come in for the right reasons, you are on your way to a great event no matter what the arena.