I loved the first two seasons. I binged all three compulsively, and watched the first two seasons a couple times. The third season really brings it down though.
The biggest let down in the third season is the the excessive mawkishness and the narrative that doesn't really go anywhere. Maybe there is a point to that, not everything is linear in life. We don't always have a realization and then change for good. We change, we backslide, we get a little better a little worse.
Also, the atheism/scepticism conversations are a little 2006. People who believe in horoscopes are silly, we know. I went through my new atheist phase and still basically believe in that position. However, it can get a bit dull.
But I think the soppy moments are often overdone in the last season, you get moments like that which are a bit much in previous seasons but it basically all there is in the third. I feel like you could treat the end of season two as the finale and it would be more emotionally fulfilling, less boring.