Sorry, but these companies spend much more effort on making sure their product is walled off and incompatible with everything than giving it any actual quality.
You think Whatsapp for example is this lightweight and easy to use on basically any phone because no one spent a dime on some R&D on how to make it the way it is?
I am not well versed in Android or iPhone software development, but yes, I don't believe that making a non-bloated mobile app is pushing the frontier of software engineering.
There could be some arguments made somewhere as to where R&D money could go, perhaps somewhere in the backbone that billions could use, but the UI is not it.
All that said, I don't know how it furthers your initial argument exactly, as the DMA "beneficiaries" benefit from this lightweightness in zero percent. If anything, it's a negative, because one could assume they have to do better than that with what they're offering.
You think Whatsapp for example is this lightweight and easy to use on basically any phone because no one spent a dime on some R&D on how to make it the way it is?