Shadowblade didn’t really need the buff it’s getting but at the very least it should still require concentration even if keeping the duration infinite until long rest, no concentration needed is a massive buff it didn’t really need.
Meanwhile flame blade should receive the same buffs shadowblade gets if any of the buffs for shadowblade are staying in, of the two flame blade is the one that underperforms normally and needs buffs to help it if either of them do. Flame blade should also be on the sorcerer and Wizard spell lists as well.