I have the opposite view.
Based on my current home, bought in 2001. It was built in 1974 and the small GE under counter microwave must have been at least 5 years old when I moved in
I have had and replaced three top of the line large microwaves in the last 13 years, and that little GE just keeps on waving. And its function buttons are the most intuitive I have run across.
You might have one of the earlier 915 Mhz models. Those are industrial grade. LoL