I guess I should rephrase my question.
1. Is the game fun to play with zero save-scumming (going back to earlier points when the result of an action is undesirable) and perma-death on?
2. Does the game have a lot of grindy/chore-like tasks required to build characters? Or is straight-up strategic action + story all the way through? (with characters growing in stats along the way)
1. You are about the only person I know who pushes onwards when a unit dies whereas everyone else starts the battle over again. As for your question, no. Three Houses has one of the smallest casts in the series (29-31 characters depending on the path you take) and the recruitment process has a lot of requirements that aren't easy to meet on the initial playthrough, so chances are that you'll have access to 20 or fewer units, leaving not much room for error. New game+ helps to recruit people easier.
2. Building characters can be sped up by skipping the thorough exploration of the monastery each month and only doing the most important things via fast travel within the monastery. It's also possible to skip right to the end of each month in which case the game automatically assigns skill EXP to the two skills that are currently selected for each character. The risk of skipping is that it gets harder to recruit new characters. Overall, Three Houses has easily the most non-battle time of any game in the series.
So many different opinions, who do I listen to?
Any Blazing Blade fans want to speak to this game? And I mean the sorts that REALLY hated Awakening (I'm not one of you, I liked Awakening, but I am very very sympathetic toward your opinions).
Regarding story and characters, you are getting a strong package. But as mentioned above, there's also quite a lot of baggage attached to enjoy the game to its fullest. I wouldn't mind if the free-roaming in the monastery had been replaced by menu-based actions, such as base conversations in Path of Radiance and Radiant Dawn where only characters who have something to say between chapters get some spotlight, as opposed to the monastery where most characters just give some short and usually unimportant commentary when you talk to them.
I don't think you'd like this game. Then again, you are totally weird.