The bit of the dialogue you quote is Plato telling a story.
On another bit he says directly: anyone can plainly see there is nothing detrimental about writing itself.
And further down the line he warns against relying on text solely to learn and not other learned people because you might lose context and internalize the wrong interpretation.
This is a great illustration of the dangers of lost context.
This excerpt is a bit of the dialogue where Socrates is quoting some legend that takes place in Egypt.
On other parts of the dialogue, when speaking directly, Plato says that anyone can plainly see that writing in itself is not negative.
There is also a great bit where he warns that relying on texts solely to learn without guidance of other learned people opens oneself to misinterpreting the text and learning all the wrong things from it.
The bit of the dialogue you quote is Plato telling a story.
On another bit he says directly: anyone can plainly see there is nothing detrimental about writing itself.
And further down the line he warns against relying on text solely to learn and not other learned people because you might lose context and internalize the wrong interpretation.
Much like you did.