I will absolutely grant you that there are a lot of practical things to take into consideration to manage the transition. And it would indeed require for there to be an overlap-period where we pay for both.

But those are merely practical issues to work with. Not insurmountable problems that should stop this altogether from even getting started.

I'll try to ELI5 it:

A police officer is basically "a guy with a gun". So the question we, as a society, need to ask ourselves is "when do we need a guy with a gun and when are we better served with a different solution."

• for things like a bank robbery or a hostage situation, a guy with a gun is great person to have. This is the kind of thing police are good for. Nobody wants to stop police officers from stopping dangerous criminals and people who say otherwise are lying to you.
• But for things like "a homeless person who is addicted to drugs". WTF is a guy with a gun going to do to help this situation?? We need trained social workers and paramedics to handle this issue, not police officers.
• Even for smaller criminal issues like a kid doing vandalism due to a bad homelife, I would argue that sending in armed forces with guns is a major overreaction that won't help anyone. We would be better served by helping these kids get a better life instead of punishing them for small misdemeanors.

The problem in the USA is that the police is currently the only solution to every problem, no matter how ill-equipped they are to handle it. We would be better served to defund them, use them for serious issues only and use those newly freed funds to invest in better healthcare, education and social workers to prevent problems in the first place.

It's a training exercise and it works the exact same way all training for anything works.

• Studying doesn't have the same stress as an actual exam, but it still works
• Training for a sport isn't the same as being in an actual match, but it still works to learn the strategy and teamwork etc.
• ...

Military exercises are the same.

It's a nice movie, but not at all realistic with how a jury actually works.

Juror number 12 broke the law on multiple occasions.