Nonsense. Ir's as useful as reading a phone book cover to cover.
Is it a good idea to read MCO cover to cover?
[Is it a good idea to read MCO cover to cover?] What do you think? I think it is a must for amateurs. ...
I haven't seen the publication of a revised MCO since 2008. Hard to believe that very many have been considering MCO to be a must.
... [MCO] Gives you a good overview of all the opening systems without the danger of being confused by the complexity.
Since 2010, has there been any publication of a new book attempting to provide an overview of all of the openings?
"... For new players, I cannot recommend books that use [an encyclopedic] type of presentation [of opening theory], because the explanatory prose that elaborates typical plans and ideas is usually absent, thus leaving the student without any clear idea why certain moves are played or even preferred over other apparently equivalent moves. ..." - FM Carsten Hansen (2010)

Only if you really want to!
A few people in the world have extra strong memorization capabilities, and you may be one of them.
- Nigel Richards, the best Scrabble player in the world probably. he can memorize the word lists very, very well. He switched from the English International tournament word list to French and then won the French world scrabble championship the first time he tried. He could probably do that with MCO if he wanted to.
- People who are undergrads at MIT, according to legend.
- Techies who are really worth their money, like maybe Elon Musk (before the marijuana) or similar. I read somewhere that if you give some people a big technical manual they can know all the contents within a couple days or so.
So if you are like them, and you have already conquered enough other technical areas, then you might choose to memorize MCO as your hobby.
For another example, there's a book from 2009 I just finished reading, called The Big Short. One or two of the characters, fairly odd individuals, decided as a hobby to thoroughly understand the housing bubble, and they succeeded. One did it by being the only person in the whole country practically (including, significantly, the bond rating agencies) to read the detailed information in every related bond offering, describing specifically what mortgages (and other shaky bond offerings!) (and other even more shaky bond offerings, and on and on!!!....!!) were inside each of the "CDO"s in the whole crooked tower of lie lie lie bonds! great read.
Anyway, if you are like that, I guess go ahead and read MCO, but I would recommend reading The Big Short first. (Some of the characters may be involved with the idea of "asperger's syndrome". People with this kind of ability may be vaguely connected with that syndrome also. But that is not anything to worry about.) (Also, at the end of The Big Short, the guy who had been Right was not a popular guy.)
Good luck in your chess!
Also, there may be other databases to study that could be more effective to learn than MCO.
The End
What do you think? I think it is a must for amateurs. Gives you a good overview of all the opening systems without the danger of being confused by the complexity.