not surprised, modems are notoriously hard to design and get it right, even if apple comes out with their own, they still be paying patent royalties to QC.
This is unclear. How many companies in the world make modems?
The big relevant ones are: Qualcomm, Samsung, Huawei, MediaTek. (There are a few smaller less well known ones, and many other companies that produces parts of the "5G system".)
All 4 ship modems that work adequately within their target use cases.
So basically all one can REALLY say is that "Intel found it hard to build a 5G modem", not "it is hard to build a 5G modem"; and that may say something about Intel (purveyor of such fine products as Itanium, Quark, Habanero, Optane, and 10/7nm processes).
Modem design seems to be the latest version of what was CPU design and then GPU design: a field where few understand the details, but everyone's enough of an expert to make wild claims like "no-one can enter the market now because all the good ideas are controlled by patents, and every aspect of the problem is so complex".
Honestly what I find more interesting (and worrisome) is the lack of progress Apple has made in incorporating more WiFi and GPS tech into their other chips. For example, it seems like they should be able to provide more advanced WiFi or GPS (without cellular) on Apple Watch. Even if those are not great implementations, they do provide real world testing of the functionality in a lower stakes environment.
Maybe the patent issues mean the per-unit cost for adding this functionality is not minimal? Even so, the lack of progress on WiFi and GPS (as opposed to constant improvement with BT) is where I'm concerned. No-one expected cellular to happen fast, but starting small and growing each year is feasible for GPS and WiFi.