The truth of the matter is that the documentation of a product should be excellent. The grammar and style should be flawless and the information should be easy to read and retain.
Producing excellent documentation is not easy because it requires focus and a commitment to excellence, not only from the writer, but from the entire development team. It is quite literally a team effort: from the product designers, the coders, the testers, the trainers, and the writer. The documentation is the most human of all the aspects of a product because you cannot run it through a machine to find the flaws: it must be written, tested, and improved by human beings.
Bad documentation is the canary in the coal mine. Bad documentation is the absent red M&Ms. Bad documentation is the harbinger of bad omens.
If the documentation is bad, then that is a strong indicator that the company doesn’t care enough about the quality of its product from end-to-end. And you, the customer, are their latest victim.