Illogical.
"It seems that the only serious thing, a player aspiring to be a champion can do, is to hire a coach in chess."
Even so, books helping players improve is ubiquitous in chess. If you want to improve, a coach can be great. My answer to your title is "yes!"
For those not aiming for the very top though, perhaps even better is the right environment. Post mortems at clubs and tournaments are free (and often invaluable) lessons.
Reading most champions' biographies one thing which always come out is that they all had coaches.
It seems that the only serious thing, a player can do to improve, is to hire a coach in chess.
Books are mostly useless, since there is no champion who through reading books became what he was (maybe the only exception is Fischer, but 1 out of 99 just confirm the idea that coaches are the best way to improve).
Does anyone have experieces with coaches, what to ask them, how to find the right one and so on?