If you look back on SoC development it's clear that it was chaotic during the early years. The goals were over-ambitious, some aspects of the game were being developed much faster while others lagged behind, art style was all over the place etc. Lots of very basic things were left for later while the devs were focusing on minor events that suit the fanbase's fetishes or introducing completely new plot points (like Fae storyline) that are still only in the very early phase.
So yes, if someone donated lots of money for the game while expecting relatively smooth progress on all its aspects, he/she has a right to be disappointed. The truth is the devs were (or still are) gradually learning how to properly create VNs and SoC is their experimental field. But at least for 4 years now, the progress is good and stable. It's not super fast, but the quality of new content is extremely high, both in terms of writing and art. Hell, I'd pay 3$ per month on Patreon just to see all the new amazing CGs that are constantly being produced.
SoC will probably take many more years to finish, probably even more than a decade (if we are talking about three acts). But I don't really mind it as long as the devs will continue to work on it keeping at least the current pace. Even right now, far from completion, it's one of the best Western erotic VNs.