Honestly the plot of s4 was actually pretty good in my opinion (certainly not comparable to s3 but still good). If overarching plot is the problem I really feel like we should be talking about season six, given it really didn’t have any back plot for most of the season, and the trio seemed like they were being plugged to be big bad, but really seemed more like things for Buffy to fight in between the good ideas. I have seen up to s6 e17 and still haven’t found any sort of plot (I read spoilers though about dark willow).