OK, this is actually accidentally insulting despite effectively coming to a correct conclusion. Cutting to the chase: I have developed multiple extremely well-used and in one case "de facto standard" tools used to jailbreak Android devices. (I even have my own implementation of the Linux futex_requeue exploit, which is not only a really difficult exploit to pull off at all but I explained the way mine works to geohot and he found it impressive as I'd figured out a better way to exploit it than he had.)
I give talks at conferences on how exploits work, something I also teach occasionally to the Computer Science classes at the College of Creative Studies (where I am an awkward form of adjunct faculty). I wrote the first decompiler for .NET, a tool which was even used by people at Microsoft to do tests of some of their compilers for a while, so I definitely have a background in overall reverse engineering work, and I've worked on reverse engineering tools for native software as well.
Substrate itself actually requires an extreme level of knowledge of ARM, as does (I'd hope obviously) working on a compiler, which is one of the first things I did for the iOS community: I fixed up and ended up taking over (when the original developers "saw their out", made me an administrator, and none of us ever heard from them again) the alternative iOS toolchain project. A lot of the stuff I work on for this community is the low-level stuff that you are claiming is over my head.
The way in which you are likely correct, though, is that building jailbreaks is like panning for gold, and doing end-to-end exploits on iOS is extremely complex work. I was involved in an implementation of a full jailbreak for iOS 7, and as a single person I really can't do all of that and everything else; and while things are actually easier now due to Xcode 7, it is also much harder due to the kernel mitigations (like, the real issue here is that jailbreaking is too hard for everyone).
Even if I could pull all of this off myself, I probably would not want to, as all of the people I really liked in this community have left, and the people who are bothering to remain (which is kind of the correct wording: there is a lot less direct reason to jailbreak devices, at least in the United States) are increasingly argumentative. I am actively trying to find other things to do with my life. So, really: the premise is flawed; instead of asking "could", you need to ask the question "would".