Knowledgeable developers would install Microsoft' JScript debugging tools, I guess it is a bit too late to learn about them.
https://en.wikipedia.org/wiki/Microsoft_Script_Debugger
No need for genius or waiting for Netscape to come up with something.
If you work with Microsoft Office add-on dev you can still feel the echos of this with the Microsoft Script Editor.
What killed IE for me is the developer experience. To get the value of a variable you had to:
Then some genius created a JS widget with an absolute positioned floating console that allowed me to inspect variables on a basic level.Then came Firefox and it was a game changer for development. It was no wonder every web developer rooted for IE to finally die.