Prince's Ex-Manager Says John Legend Haters Missed Performance's Point

John Legend's tribute to Prince at the Democratic National Convention was good, but it pales in comparison to the song itself ... so says the late Purple Rain singer's ex-manager.

We spoke with L. Londell McMillan -- who previously worked as both manager and attorney to the ethereal star -- about JL's performance at the DNC this week ... a show which pissed a lot of people off.

ICYMI ... fans called out Legend, 'cause he sounds a lot like himself while singing, and not enough like Prince, while performing with longtime Prince collaborator Sheila E. -- and, many people felt he wasn't the right person to sing "Let's Go Crazy."

Lots of folks online were more excited about Sheila and guitarist Ari O'Neal's skills ... saying she can shred just like The Artist Formerly Known As.

McMillian's being a whole lot kinder to Legend than many fans on social media ... telling us he was at the DNC and thinks John, Ari and Sheila did a fine job with the song.

That said, LLM adds there's only one Prince ... and, one of his best skills was the ability to craft a powerful message -- a message he felt was on full display in Chicago this week.

McMillan goes on to say everyone's entitled to their opinion ... and his is Kamala Harris and Tim Walz are HUGE Prince fans -- just like everyone should be, L. Londell says.

We broke the story ... Prince passed away more than 8 years ago after overdosing on fentanyl -- and, Sheila E. performed a tribute to him then as well.