I think that the products you're complaining about are in the state they are in because of vendor choices independent of the software development process. If to

I think that the products you're complaining about are in the state they are in because of vendor choices independent of the software development process. If total stability and backwards compatibility are not design requirements, neither Agile nor Waterfall will automatically implement them for you. I think your class or professors are assigning behaviors and outcomes to development processes that should instead be assigned to the companies or people implementing them.