sagepayload artificially slows the game down for everyone even if the disparity in skill between the two teams are quite high, since you have to constantly push that cart. Besides, most payload map have huge open spaces and were clearly not designed for low population servers.
I feel like this could be fixed by either a) having the cart push itself for a while after blu stops touching it, with it stopping after either someone from red standing in front of it or a certain amount of time elapsing without anyone on blu touching it or b) making new payload maps that are shorter and quicker to finish.
I really think that 5cp is a fun game mode, but it is not perfect and definitely prone to stalemates when the two teams playing it have equal skill levels, and I think pl could and should be played in 6s, albeit with some modifications (like the ones mentioned above)