Well, Harris is good at her job, she is not good at campaigning nor debating. Again, just look at the Democratic primary where she entered as a superstar and a favorite of the party and then bombed out big time. I think part of the issue is she has been overcoached and part of that is for whatever reason...they expect that a lot of Americans do not want to hear a strong aggressive woman's voice. I guess a result of a rather costly lesson learned running Hillary Clinton. However, Harris is not Clinton. Clinton entered the presidential contest as one of the most despised candidates ever to run. She was a horrible choice because  you lost voters of every stripe running her. Despised by Republicans, Independents, and Democrats. She had a base of support from centrist Democrats but she never could branch out beyond that because the country mostly did not like her nor trust her. 

If you want to know why Democrats love Harris, look at her performances in Senate hearings. She is fantastic making people like Bill Barr, an extremely slippery snake, look like the lying assholes they are. In these hearings you would get a lot of blah, blah, blah grandstanding from most senators but Harris was always intelligent, to the point, and asked the good questions. Get her on a campaign stage though and she is not the same person.  I think this likely comes from overcoaching, attempting to give her a softness that consultants see as required from a female candidate. Basically, I think you are correct that the coaching was inept because it takes away her greatest strength...she's a strong prosecutor. They should have said "prosecute Mike Pence the way you did Bill Barr" and let Kamala be Kamala. 

Trump intentionally tried to turn the first debate into a shit show so he was not on his heels all the time responding to what a horrible job he's done and how his primary policy is to always be dishonest with the American people. He did not want to talk about his taxes, his failure with Covid, his thousands of lies...so he went all circus freak. 

Now, in a debate you are being asked questions that you need to answer...and the big thing that Harris and Biden have in this situation is THE FACTS ARE ON THEIR SIDE...but Harris could have been coached to act like the prosecutor she is and to leave pointed questions on the table in her responses. She should have prosecuted the case of Trump and Pence and the great crimes they have perpetrated on the American people. 

All that said, I thought she did fine. The facts were on her side and she did "no harm" to the massive lead the polling shows Biden/Harris has. Could she have been better and better coached? Oh yeah. 

Here's why Democrats love her and why people should have faith in her...and just watch Corey Booker sitting next to her, he's pretty much glowing because she is doing such an amazing job and Barr, who is excellent at dodging questions, gets his big fat ass handed to him...