Fans give their money (6k (!) a month on the patreon page alone, must I remind) for Radiant since it's the page for that game alone. Thus, if the updates are slow as described above, they have the right to complain.
I agree that paying fans have the right to complain. But please be reminded that they pledged the money voluntarily and some even knowing that the devs have other projects. If they are really unhappy with the progress, they also have the right to withdraw to give a piece of their mind to the devs. Or they can give constructive criticism, not whine about how long an update is taking and demand that the devs work faster and must have at least certain hours of content in an update.
If the devs are lazy / slow, penalize them. It's their own fault for not working hard enough, and they have no real obligations but ONLY THEIR OWN SENSE OF OBLIGATIONS to the fans.
The situation is similar to a manga. A mangaka can have many serialization going at the same time. But in the end, no matter how many assistants they hire, it's just one main source the content is going to come from.
If the dev team want their circumstances with other games to be taken into account by their patrons, the patreon page should be for all those games, so that the content for those patrons would be fair. And honestly, with all that money from multiple sites and multiple games, maybe hiring some people to make up for it would fix the problem.
This game is a collaboration, so it made sense to me on why they started a new page for the game alone. If I have a company and some other people comes to me for partnership into something else because of my certain skills, obviously I am not letting them into my current company but start a new one where everyone has a stake in it. So if this startup fails, at least it will not affect my other business. The rest bogs down to each partners' responsibilities to the company to make it a success.