Pretty much every character at either of the big two publishers has been influenced by a character from the other, but that isn't a moral issue so long as those similarities remain superficial as is the case.
Alternatively we can look at it this way - If Rob Liefeld can admit that 'Wade Wilson' Deadpool was a straight rip-off of DC's 'Slade Wilson' Deathstrike and get away with it, then all bets are off for anyone else!
Mart Nodell straight up said that Aladdin inspired Green Lantern. There are only so many heroic archetypes. Yeah Batman was very close to the Shadow and Superman was a combination of sci-fi and pulp ideas, but in the end it is what you do with them.
I always liked the Nighhawk of the Defenders, and superficially he was very much Batman, but once you dived into the character he became is own and very interesting character.
A good writer can always find a creative way to make a story more unique, no matter what it is.