Oh no. How did we ever live without companies spending money and effort between the invention of computers and now.

We didn't. There has been constant innovation from then up until now.

Indeed. Yet you claim that opening platforms somehow prevents companies from investing in R&D

It does when a company has spent R&D to create a closed platform specifically for their customers. The closed platform is Apple's USP, their features are better because they only have to develop and support them for their devices.