TLDR; Mixed feelings resulting in a positive overall view of Welcome to the NHK. I hated it but loved hating it. It achieves its goal and is an excellently written, grounded story.
Never been so conflicted over an anime, its portrayal of some tropes and real life problems are so real that it honestly is unenjoyable and a hard watch at points. It doesn't fall into the overly idealised version of stuff that most other anime do. Which I appreciate.
Anything that can make me think this hard after watching is pretty fantastic in my opinion, I hated it at points yet I find myself wanting to watch it again a day after finishing it. I didn't hate it for the writing, I hated it for the very grounded and oddly realistic decisions made by the characters. You'll find yourself getting annoyed at the characters the same way you do actual people. More stuff I loved about the characters is that each arc isn't on the nose or overly explained at all, there isn't any "wow he/she has come so far" or any 'checkpoints'. It takes a step back and is more gradual. It lets the audience piece it together, giving the audience 2 + 2 instead of 4 is something I greatly appreciate in a show.
I like to think that the message is that some things don't turn out good, nor do they last forever. Everyone has their own individual struggles that others can't possibly relate to, but instead understand (to an extent). I found myself very tied to and rooting for all characters no matter their morally grey position. Can be summed up entirely as 'painfully realistic'.
I highly recommend it for anyone in a good mental headspace for sure. If you're not, maybe steer clear. Its pretty heavy and has a melancholic tone (bordering on depressive).
8-9/10, pushes into 9 territory as its the first time I've ever felt the need to review an anime.