I have just been watching the early season 6 episodes again, first time in years, except for the bargaining two,which are just scene setters to me where nothing much happens except Buffy is brought back in a long protracted sequence.
The 3 episodes after that at least so far, having just rewatched them, Buffy/SMG does a great job setting up the depression arc, its not just depression, but existential despair. She is facing the complete meaninglessness of existence after having done what she felt completed her existence at the end of season 5. First they have to face the demons they raised by bringing her back. Next, she finds herself "flooded" with life's inane everyday responsibilities. Then she faces the monotony of various jobs trying to find a place for herself in Life Serial. You may not like that they decided to do this in season 6, but I think you can say they executed it very well, particularly during this phase of the series.
One element I do find odd is this sudden trust she has of Spike, I cannot understand why she feels able to confide in Spike, but not in Giles. Yes, I can understand why she mistrusts the scoobies a little bit for bringing her back, and she can't unload on Dawn. But, with Giles? Maybe it goes back to the argument they had end of season 5, where Giles wanted to consider the option that they may have to kill Dawn. Other than that it could simply be a matter of they had to find ways to distance Giles from the storyline due to him not being able to act as much on Buffy during this season.
I too am one who has liked this season compared to some others. I love the emotional roller coaster of it. I find myself watching getting angry at Willow at various points because of her childish naivety about her use and abuse of magic. I feel for Buffy and what she is going through. And I love the reconciliation at the end between Xander and Willow. Human vulnerability on full display. It gets me emotionally involved. It was something different from the usual imperturbable hero-types, it made a refreshing change. Yes, it meant Buffy had to take on almost a supporting role towards the end, due to the power of Willow. But this was all part of what season 6 was about. Power was not going to be the solution to the depth of problems they had got tangled in this time. It took rather Mercy and Forgiveness.