One thing I do know is that groundschool and associated technical training has been repeatedly cut over the last forty years as airlines, in particular, seek to reduce costs.
Unfortunately modern aircraft systems are too complicated to be gone into with the level of depth required for a full understanding of how and why to be imparted to a millennial who couldn’t even change a wheel on a car. Ground school would take several months and require a reasonable understanding of electrics, hydraulics, pneumatics etc before it could even be attempted.
System information has been reduced to “this black box does this” in the pilots manuals, with more detailed information only available in the engineers books.
The days of a ground school having engineers using actual aircraft parts and demonstration boards to explain aircraft systems are nearly over.