Unless I misunderstand this, the problem with Multi-Account Containers is that sites sharing the same container can read each other's cookies probably because MAC is actually designed for multi-account scenarios rather than to isolate each site. I wish there was a way to containerise each site by default without breaking the web.
Konform Browser
Looks good but I would miss new Firefox features and the stricter the restrictions the more friction. I used NoScript for a while in the past and it was a nightmare.