I'm a little confused about the "can't shoot at an elite level" part. Who are you referring to there? MJ had better touch in the midrange than LeBron has/had , but obviously he was pretty bad behind the three-point line. I tend to give players of that era more a of a break though when it comes to three-point shooting efficiency though
LeBron obviously isn't close to an elite shooter. He's gotten better but he's still average. That could be viewed as an argument in his favor though because he is dominating the time period where outside shooting matters the most.
If he got to play in a time period where his biggest weakness didn't matter as much and 1 of his biggest strengths (his physicality) was able to be used more effectively (with rules that allowed D to be more physical) he would be even better in that time period.
As far as MJ or other guys not hitting 3's from that era. It's just why comparing eras is largely pointless. Most of those guys didn't even have a 3pt line in High School and their 1980's fish college coaches told them the 3pt shot was "a sucker bet", it was just a weapon that was before its time back then. I'm sure someone like Reggie Miller looks back and thinks "damn, I was 20 years too early"