Christopher
Tolkien’s instroduction to
The Book of Lost Tales 1 is in part in response to negative criticism and often wrong-headed criticism of the published
Silmarillion.
People did have difficulty into getting into it, a difficulty that would have been alleviated for some had it been presented in a framework in which it was shown to be a summary of more extensive legends.
J.R.R. Tolkien considered the
Silmarillion to be an existing chronicle within the world of
The Lord of the Rings, but within that world to be garbled legend rather than history.
Obviously J.R.R. Tolkien did intend some sort of introduction of that kind, so set the work in a context, without which there is a certain lack.
Christopher Tolkien might, for example, have reprinted the Note on
Shire Records, followed by some of his father's remarks discussing the legendary origins of the
Silmarillion material that now appear in
Morgoth’s Ring.
This, without any invented editorial additions by Christopher Tolkien would have provided the missing framework.