To put in my two cents on Megalo Box since I've complained about it's aesthetic before, I think there were two big miscalculations.
The first I feel was the decision to keep the show at 16:9 despite the downgrade to and then rescaling from 480p. Condensing the frame to 4:3 would've cut down on the blur effect and the jagged edges to the line work that resulted from the process, and would've more accurately represented the time when this aesthetic the director was going for was big. That said, that was a decision that would've had to be made at the beginning of production, because if they had cut the ratio after building the scenes at 16:9, they would've lost over a third of every image.
Second, the show doesn't have the one thing I think defines cel animation over digital: high contrast images. I remember watching Akira last year for the first time since it had been released on BD, and the thing that stood out the most is how much the colors popped off the screen in comparison to a lot of modern anime. The way light filters through a cel and through the oil painted on to it is something that's incredibly difficult to reproduce digitally, but messing with the contrast to widen the disparity between the bright colors with the darker lines would've been a good step. Instead, the blur filter ends up having the opposite effect, washing out the image and making things look grey. As people have said, it looks like a cel-to-VHS transfer, and it just proceeds to make the assets that have already been tampered with noticeably worse.
The problem with all of this is that the show has really nice production design, and there's some great art here. But in chasing an old aesthetic without maybe properly understanding how to replicate it, the show is sabatoging that art for the sake of a style that doesn't quite convey what I think the director was hoping it would.