The aim has always been to get city happiness management to the point where only the poopiest tundra cities are going to need the help that a PW provides if a skillful player is managing their empire well.
That Having Been Said. PW need to be effective. They need to be usable. They need to be tangible. Then, balance happiness around the goal that Emperor+ players will choose to build something that actually provides yields over PWs 99% of the time. If people who don't know as much about the game aren't supposed to use it then
it shouldn't exist. If it exists then it should be at least viable. Sub-optimal, sure, but many of you are basically arguing that PWs should be either
garbage or Byzantine, in which case they are just a n00b-trap and a source of impotent frustration.
I agree with
@Enrico Swagolo that scaling PWs on era feels like an unnecessary punish for people who resort to PWs (ie. n00bs), because it chastises them for not having predicted a happiness problem 1-2 eras ago. Scaling by number of previous projects should be sufficient.
Another unnecessary double-punish for n00bs is no flat

unhappiness reduction; people who aren't on the forum have no idea if they are even working unless they see an immediate bump in

on the top bar.
People like
@Recursive and
@Txurce are talking about how we need to make these PWs as peripheral as possible. But... Why? Or perhaps more accurately, How? And how are we going to communicate that? Are we going to make the button on the UI smaller so n00bs will click it less, or bury it in some sub-menu? Or perhaps make the project contextual, requiring a certain level of global or local

unhappiness before it can be built?
If we can agree that VP is more for the thousands of regular downloaders who don't speak up, rather than the few dozen of us here who do, then I think we can agree that PWs need to become more accessible and their benefits need to be more tangible. I'm trying to get my wife into this game and sometimes it feels like people on this forum are kneecapping me by lobbying for the obfuscation of these sorts of on-ramp mechanics.