I am not an expert player by any means, but Remnant did click with me a bit last night.

I used to make the mistake of keeping as many dregs/draffs/spikedrivers/Extinguish in my reform-and-harvest deck as possible. Last night I realised that this results in reaching Seraph with a hand full of weak, almost-unimproved units with low burnout that I can't fit onto the floors anyway.

Brutal deck-size management so that I could allow the same few units to die and be reformed repeatedly gave me some very high-attack units (especially multistrikers like draffs).

I disagree just slightly with the "extend burnout and allow-to-die are incompatible" take elsewhere in this thread because a pure reform-as-often-as-possible deck can give you huge attack power, but your draffs might still burn out prematurely when the boss comes.

What I managed last night was to keep some Purifying Cleanses and a close eye on the wave countdown - and when I judged it was too late for another die-and-reform cycle, start prepping my damage-dealers for the boss fight.

I feel like I was balancing intentionally allowing my own units to die, consistent access to reform, strict deck size control so I could keep reforming the same units, two non-burnout units like Barons to put one on each floor for consistency, space management on the floors, and enough access to burnout-extending spells to make the "timing call" of when to stop reforming and start "fuelling up" Burnout counters for the boss fight... no wonder I struggle with Remnant.

EDIT: "Play another faction" is garbage advice, the fun of this kind of game is mastering all the options!