As a non fanboy there might be one of numerous legitimate reasons for going to a pay to play format. They may be unable to support development without money, or maybe they want to be able to live somewhere other then mother's basement, or possibly, just maybe, they've finally gotten to a point where they feel justified in asking for some money to be able to play the game fully. I don't get why people are mad, these guys have put a lot of effort into the game from the sounds of it so why not pay some cash if you enjoyed it? Other niche games have done similiar if I recall correctly, so it's not like this is a new thing where a free game went pay to play.
I'm far from a fanboy of Haven and Hearth, as a matter of fact I found the game to be like Farmville with Dwarf Fortress elements. The problem with Haven and Hearth (they did this for balance and "realism") is that you have to wait, a lot, like stupid amounts. Do you know in F2P games where you have that one building that gives you loads of money, but only works in 2-3 days. Well take that idea and apply that to getting something as basic as leather, or smelting ore, or basically anything that's required to get far in the early game.
So they put up a pay wall basically saying you get a few days a month to check your settlement and finally get to play with all that stuff you spent so many hours collecting. This basically means that if you go the Free-to-Play route, you have two days maximum to gather all the supplies you need, and try to get them prepped or hidden away well enough, so that when next month rolls around you can finally play with what you got. But there comes the problem of other players. While you're basically in a month-long coma, you can get murdered, raided, and have your stuff griefed.
So if you don't pay the $10 for your pay-to-win coin (yeah in order to extend your time you can pay $10 bucks for an in-game item that basically lets you have an extended trial period, the idea is to have people in the game trade fuck loads of items with each other to get this "life extension" coins), but why do that when (if you have a subscription, which is $15) you could just raid the trial-boy's home and loot all his shit that way.
I don't give a shit how desperate for money you are, you don't shaft half your fanbase, silence complaints, and just let the people carrying banners in your name keep cheering on. You know what happens on Steam when shit like this happens? Youtubers and press get a hold of it and make you look like something worse then Hitler.
They could've easily warned the community about the impending change, explaining everything, and been open to criticism. Because this exact business practice is what killed their other MMO that was about the Salem Witch Trials or something (it was basically, Sexy Witches the MMO).
The best way to implement some form of subscription fee for Haven&Hearth wouldn't be holding your shit hostage for the rest of the 28 days. It would've been better if they restricted higher levels of tech to paying players, stuff like steelworking, that magic system no one really uses, and mining. Basically the stuff that people with plenty of time and dedication to the game would pay for. While the new players could get a good taste of how the game works for plenty of time, and when they're ready to progress to town/civilized tech and materials. They shell out the $15 bucks a month to enjoy the more sophisticated side of the game, where PVP battles are everywhere, and people operate full kingdoms from their skull throne.
Because getting out of the early nomad stages where you live in a grass shelter, can't hunt, and all you can really do is look at thing to research stuff in order to get some form of progress (which can take minutes, hours, days, or weeks); is a long, long process that requires ridiculous amounts of coordination and cooperation.
Better analogy: The Nomad early stages are like a tutorial, while the town, pvp, kingdom building stuff in the "late game" is like the full game. So allowing people to get far enough to the "Civilized stage" and then making them pay for the game would be more then fair at that point.