Her voice is fine, imo. She's 58, she's not going to sound the way she did in 1995 plus live vocals always sound significantly different to studio vocals. Very few singers can reproduce the sound of the studio version of the song. Men and women both experience a lowering / deepening of the voice as they get older which is why singers sometimes have to change the song into a different key in order to be able to sing it live. Sure there were a couple of notes that she didn't quite reach, that's pretty normal.
I haven't watched a lot of Janet performing live. Afaik, she does use pre-recorded vocals on some of her songs. But it's still her mature voice that her audience is hearing.
Personally, I enjoyed it.