Is "Message List Display Options -> Table View" not pretty well exactly what you want? I enabled it (on desktop) shortly after the roll-out, and I've never had it revert back. There's no CSS hackery, no forced reversion, not even a hidden menu - Card vs. Table view is a top-level menu item.
Telling me "There's no way to revert it" feels like, at best, giving up at the sign of the smallest difficulty. At worst it's a bad-faith argument, as it's clearly possible - and fairly easy and straightforward, IMO.
Mozilla themselves called it "Rebuilding The Thunderbird Interface From Scratch", and as we know, rebuilding something from scratch is a great idea, and improves the product on all metrics always.
In my opinion, it's a travesty. I refuse to use it. I would rather use broken Kmail.
Telling me "There's no way to revert it" feels like, at best, giving up at the sign of the smallest difficulty. At worst it's a bad-faith argument, as it's clearly possible - and fairly easy and straightforward, IMO.