I'm sure some people are being ridiculous and talking about that extreme (legal action), but most people are just annoyed that he's piecemealing content out bit-by-bit and can't even update according to the parameters he's set.
Don't mix "wow, a delay even beyond what he stated - I bet we'll get like two bugfixes" with "omg, I'm going to sue this asshole for taking my fucking money every month" and act like the latter means criticism in general is entitlement.
When you fail to do your job, you generally face angry people. His job is to create the game - he's getting paid to do this and requested money from followers explicitly so that he could focus on the game rather than other paying projects and put "long hours" into it routinely. He also set his own release schedule and placed those delivery expectations upon himself.
Working from home/not a traditional 9-5 doesn't mean this isn't a job without expectations. Whether you're working a part time job or a full time job, you generally have to stick to a schedule and get work done, and that holds true across pretty much every single industry of which I can think.
It's not about people being mad they don't have the content "when they wish to". It's about them being upset that he's failing to do the things he said he'd do when he asked people to financially support development. His Patreon isn't a "hey drop a few bucks if you can" kind of deal - it's specifically a "pay me for this game so that I can work on it" setup. When that happens, the game ceases to be a hobby to which fans have zero right to expect be improved and moves more into a business transaction, be it legally defined as such or not.
Additionally, delays wouldn't be this much of an issue if he was actually releasing new content, but he's not. We get maybe a few lines of text an update and some bugfixes. And while those are important aspects of an update, they're hardly worth the money he requests people to send him. That's why people are annoyed - they're not getting content and now they're not even getting the new version of the game on time.
FWIW, I've played this game since soon after the first version was released and love it, but it hasn't changed much from then to now if we're being honest. There have been some expansions for sure, but the game has been in development for seven fucking years - it should have a lot more content than it did even three or four years ago. And if he can't commit to the game, then he should shut the patreon down entirely and stop taking peoples' money under the guise of game development. That way people really don't have a right to expect updates and he can do whatever it is he wants to do.
Not sure why you're being deliberately obtuse about why people are upset. It's absurd to whiteknight a game developer who is facing valid criticism.