The perfect case would be if someone is great at research and also great at explaining. But great skills are rare, and specific combinations of great skills are even more rare. So you will have a scientist or two who are great explainers at the same time, but then you have a lot of scientists who are great at research but suck at explaining, and also a lot of people who are great at explaining but suck at research. How does academia reward them?
The ones with both skills will get the highest rewards: they will invent lots of cool stuff and describe it clearly, so they will get many citations. But there are only a few such people per generation. The ones who are good researchers but suck at explanation can still invent something and publish the type of paper you complain about; and they will get a (smaller) reward for doing so. The ones who are good at explaining but suck at research... will probably be fired.
There are a few things that a person whose only skill is explaining could do in academia. They wouldn't get a reward for explaining someone else's paper clearly, but they could get a reward for writing a meta-review that would explain multiple papers clearly. In theory, their scientific contribution would be in comparing the papers, but in practice, hopefully even people who only needed one of the papers would cite them as a reward for making it easier to understand. -- I don't know if this would actually be sufficient to survive academically.
People who are good at explaining can also make money by writing popular textbooks. Question is, whether there is a sufficient demand for a popular textbook explaining some obscure math.