With all your examples back to back, I think I can pinpoint now why the Reincarnated as a Sword illustrations fell so flat for me. It's the lack of expressions. You have an inanimate object and an expressionless girl, so it's to be expected, but the only illustration I liked from the ones you posted was the last one at the table while eating. and on the flip side it's probably why I cherish the Bookworm ones so much because there is always such a high emphasis on the character's expressions.

I’d rather have the Solo-Leveling cover art ...

I have always found the Solo Leveling covers to be strange for a series based on source material, where the visuals play the most important role.