One of my bigger complaints with the game, honestly.
If you grind a decent amount of cash by, like, redoing the Test Pilot AC mission (~$55,000 IIRC) and buy a variety of weaponry and parts, then the game flows much better. Die, slightly adjust build in the menu based on needs, resume. But before you have a stockpile of money (and/or parts) you have to exit the mission entirely, sell off parts at a 1:1 valuation, buy different parts at a 1:1 valuation, re-enter mission, redo up to that point you died,
then experiment more. Just an added step that really doesn't need to be there, especially since the distinction between "AC Mission" and "Souls-like Boss" leads to wanting very different approaches
(at first) for different sections.
I whined about the game a lot last year.