First off: My disappointment surely stems primarily from the fact that this game has been described as a Demon's Souls-like. Despite its name, Archthrones is not that.
Initially, I was optimistic. A great title screen, the armors in the character editor looked great. The game starts with a Demon's Souls reference - fantastic. However, I quickly had to realize that, apart from the superficial aspects, Archthrones doesn't have much to do with the game design of Demon's Souls. And this is definitely not „the new Dark Souls 4“. I know it's unfair to measure Archthrones against FromSoftware's masterpieces. Essentially, this is not much more than a few reworked levels from Dark Souls 3, a few new levels (which have significantly less quality than those from FS), and bosses whose movesets have been randomly mashed up from known bosses. The animations have been shamelessly taken from other games. To the point where a cease and desist wouldn't surprise me at all. (Although the recontextualization of some bosses is cool.)
Unfortunately, it's also evident that they didn't understand what makes Demon's Souls level design unique. Because this doesn't have anything to do with the shortcut-based design from Demon's Souls. The reworked Dark Souls 3 levels are at least visually well done. But gameplay-wise, not much changes aside from different enemy placement.

Tldr; Archthrones is nothing more than a level overhaul for Dark Souls 3 with randomly thrown together boss encounters from other FromSoft games. Unfortunately, very little here is based on original ideas, and there's an obvious lack of understanding of FromSoftware's game design. Those who don't expect too much might still have fun with this. However, this mod is being promoted on the official website as a new game heavily based on Demon's Souls' level design. And in this regard, Archthrones fails miserably.