Coaching isn't necessarily about turning people into world class players. There's load of mundane tasks that coaches have to do such as fitness drills, fundamental drills, positioning drills.....basically drills in general. If he's crap at coaching then he can easily do some of the lesser tasks as the club will still benefit from his presence (as mentioned earlier). Even playing against him in a match would help a youngster learn.
People are talking as if every coach needs to be world class at everything, which isn't true. They just need to be be able to contribute to the coaching team. And if Stevie is able to attract new players and/or inspire youngsters then he's well on his way to being a positive influence without us knowing anything about his coaching skills.
And I'm aware this might be a contentious sentence, but I trust our existing coaching team (and even the board) to not hire someone that will bring more negatives than positives to the club. So if Klopp wants him for the first team or reserve team coaching staff, or the academy want him for the kids then I think he brings many obvious benefits and many potential benefits.