The volunteer collective, known for producing flags, banners and tifos that have earned praise from manager David Moyes, said their decision followed a chaotic conclusion to the summer window that saw Iliman Ndiaye and top scorer Beto both depart, while a late move for Monaco striker Folarin Balogun collapsed entirely.
The group had previously received backing from the club itself, including a trial that saw 50p from every discounted pint sold at Hill Dickinson Stadium donated toward their efforts.
In a statement, the 1878s said the scale of their frustration had grown significantly in the space of a single day.
"We thought the potential sale of our biggest young talent was bad enough, but the last 24 hours has topped that," the group said. "On Saturday Moyes said 'I don't think we can afford to lose any players, we need to stay as strong as we can' - since then we have lost another five players, three of them who have left play in areas we needed to strengthen in, and only brought two in.
"To leave us with no back-up full-backs and just one striker is full-on gross negligence, not forgetting we also lost one of our best players at an undervalued price in today's market in the process without replacing him too."
The group made clear their frustration was aimed at the club's decision-making rather than the players themselves.
"To be clear, this is nothing against the signings we have made, we welcome them to the club and wish them the best of luck here," the statement continued. "However, like the rest of our fanbase, we are utterly disappointed and disgusted with how this transfer window has gone, especially the end of it.
"We stated on Sunday that we do not feel that our fanbase's ambitions and the club's ambitions align right now - what happened yesterday has proved that even more."
Despite standing down from their matchday displays, the group urged supporters to continue backing the team on the pitch.
"Despite how we all feel we still urge fans to get behind our team on the pitch for 90 minutes like we did at Bournemouth on Saturday," the statement concluded. "We will fully support any action the fanbase takes in reaction to this extremely poor transfer window."