He was menacing but not menacing in the way we're supposed to expect from Lex.
Let me put it this way. Had he not been introduced as Lex Luthor, then ok, I can say that he was a great character but because he is introduced as Lex, I can't look at him that way in my DC multiverse. Unless it's revealed the DCEU Earth is a dud earth.
Sadly this is coming from someone who was ok with Evil Batman from Earth-99 even though we all know fans wanted Conroy as good Batman.