You have no idea how modern technology is produced. Any particular product is usually the result of dozens to thousands of iterations, some funded with public money and many not. Let’s take an example from your chart: DRAM. I actually don’t know when DARPA “developed” DRAM (since DARPA usually funds private companies to do development for them), but it must have been before 1970 when Intel designed the 1103 chip that got them started. Do you think that pre-1970s design is remotely similar to the DRAM operating on your device today? I’ll give you a hint: it’s not.
And no, modern device development does not consist of gluing a bunch of APIs together. Apple maintains its own compilers, languages, toolchains, runtimes, hardware, operating systems, debugging tools, and so on. Some of that code had distant origins in open source (e.g. webkit), but that’s vastly different than publicly funded and those components are usually very different today.
They’re failing to produce competitive modems because modern wireless is one of closest things humans have to straight up black magic. It’s extremely difficult to get right, especially as frequencies go up, SNR goes down, and we try to push things ever faster despite having effectively reached the Shannon limit ages ago.