Why can't academic papers in STEM be written as lucidly and easy to understand as blogs on the same topic are?
This is because academic papers and PhD dissertations are written for libraries only.
Not for real people in mind.
They don’t care if anybody reads this paper or not.
They don’t care if anybody benefits from it or not.
Of course there are exceptions (and I hope your professor is the one).
It’s rare that an academic adviser demands a clarity and simplicity of language.
Generally speaking, the more complex language you use, the more educated you appear.
With blogs it’s different. They are written by real people to real people.
Hopefully without advisers.