Edit to add: Utilizing a telephone is a significant quality of life upgrade from my (and many other) end-user experience. I'm guessing you are not Type 1 Diabetic (apologies if I am incorrect) in which case you have no idea the number of times in a day that one checks their blood sugar, boluses, etc. Frankly, it's exhausting. Being able to dial in a bolus or view my blood sugars from my phone, versus pulling out my insulin pump, has a significant impact and provides significant benefit.
Safety critical software wants to be simple and self-contained. I don't work on medical devices, but I have worked with safety-critical software before. While I know compromises are always made in practice, I would naively expect an insulin pump's remote control to be a few hundred lines of very-intensely-vetted C running on the bare metal of a microcontroller. I don't understand what a general purpose OS (!) connected to the internet (!!) is doing in a tech stack that someone notionally had to prove was safe under a wide range of circumstances.
It may be paranoia arising from my particular background. I just find it very surprising that the sheer number of layers in an app is considered responsible and appropriate engineering for the use case.