I agree with you that the pacing in Charlotte is bad. It could have been better if they gave it more episodes and focused less on comedic episodes.
I personally dislike Clannad. The characters are way too underdeveloped for my tastes. You could literally place these characters in any other anime and it wouldn't change the story. But I also just didn't find them interesting. I can't get attached to a character I don't find interesting. So even though the events that happen are sad I don't get hit with the emotional impact because I don't feel any emotional connection towards the characters in the first place. And thus, the story doesn't do anything for me. The only thing that I really enjoyed about the series was the opening songs, otherwise I just felt completely bored the whole time and only continued watching to see if it actually got any better.
Same here. Only reason I'm watching After Story - and I have it on hold rn - is because my friends tell me the first season sets up the characters for the second. I'm around a quarter through, and I still don't feel anything for the characters. However, the dull atmosphere, at least for me, has lifted a little bit due to some of the events in the second season so far.
It pretty much stays the same. It's also pretty predictable too if you haven't already been spoiled about what happens. It pretty much just gets to the point where you're just watching it to say that you did and to further validate your opinion of the series. And then people can't try say "your opinion doesn't count. You didn't finish the series."