The first time an airline pilot flies a new aircraft type in the real world they fly it with a plane full of passengers. All the training up to that point is done in a simulator.
Now that first flight is with an experienced training captain but the point is the simulator is good enough that the FAA has signed off on using that as the primary training device.
It's been this way for at least 25 years.
Many of the crash reports from the likes of Mentor Pilot on YouTube call out insufficient type-experience as a cause of accidents. Sometimes it's "the same" type, but the manufacturers manipulated the situation, the changes mean unfamiliarity and that leads to deaths.
Not giving pilots live training on new types is for financial reasons. It doesn't cause more deaths than the cost differential between training and compensation allow for.
no airline will take the risk. they will have a check ride, with an instructor.