I've been understanding of all of these things and backing it for well over a year. If you're a patron as well you just have to look at the handful of us actively making comments on the patreon updates. We're supportive but making it clear this is too long between updates, especially given content (allegedly) has been worked on. I've never been keen on this Labyrinth thing. In my posts on here I've openly talked about how much I'm looking forward to the possible content ideas (hopefully) to come AFTER this.
I'm aware and even stated in this thread multiple times I'm aware that they've been fairly transparent, but from previously Threshold had flatly said they were looking to possibly do an update after floor two (as he'd supposedly not put together what he wanted to do for the other two at the time? idk but still a let down). Basically a year between ANY updates for a piece of content few if any of us are interested in aside encouraging this expansion type content by being nice to Thresh.
I agree with you on a ton of fronts. Although, I'm not a patreon backer, I would have bounced out after 3 months without content updates (since his last one). Additionally, I'm not excited at all for the Labyrinth. It's Pac-man in RenPy... not very engaging for a battle fuck game. I'm also really not into Wolf Girls, especially these three designs I've seen.
If I had to guess what happened, Thresh got burnt out initially since he had implemented a super consistent game play loop. Basically just got bored of doing limited dev work and mostly char/story design. I think this is supported by his most recent updates, which all really do push the RenPy engine as a whole. But as a result, he's had to commit a bunch of time to the dev components, which aren't easy and put the writing on the back burner. Then fell into this even worse slump of trying to overcompensate for the amount of time he took/is taking. And now we're left with him wanting to do a full Labyrinth release that will probably disappoint everyone.
With that being said, I do wish him the best because this stuff does happen. Seriously, I have mad respect for him as a dev. However, his patreon supporters are either puffing copium or are just being too kind at this point.