100% agree with you. Loved the first half and was really let down by the 2nd.
The only other show that's given me similar vibes to the 1st half of Frieren was Violet Evergarden. Not so much for the content but in the melancholic, beautiful-yet-bittersweet vibes the whole show gives off.
I think that show greatly benefitted from the limited runtime though and would have suffered if they'd tried to push it out to Frieren length.
Really? I'm super curious what made you feel this way. I have to say I was pretty underwhelmed by it compared to Flanagan's other series'.