Opening folders while dragging and dropping

In addition to what jeffreythefrog said:

a) you can manually force a folder to open (or to open sooner) by pressing the space bar - i.e., drag, and once the target folder highlights, press the space bar to open immediately

b) check your settings in System Preferences->Accessibility->Pointer Control.

Make sure that "Spring-loading" is turne on, and adjust the speed as desired.

it appears to be working fine here. I think I would try and Start up your Mac in safe mode. then test again. if it works in safe mode, then restart the Mac normally and again test the issue. sometimes a safe boot followed by a normal boot will clear up issues. but if it doesn't work properly when restarted normally, please let us know as there are other things you can try.