I think what's being referenced by "more/less evolved" is increasing (maximal) biological complexity. Equating complexity with evolution as a whole is scientifically misleading, but it is a sub-process.

: There is only ideal adaptation to a particular environment, and environments change all
: the time.
:
: -Librarian can "accelerate" the Chief's evolutionary journey. I
: don't know what an evolutionary journey is, but evolutionary changes do
: not occur on the level of an individual within their
: lifetime...incremental changes that prove beneficial are passed on to
: offspring.

If one might expect an evolutionary adaptation to an environment via natural selection over many generations, to get that result immediately through genetic engineering is an "acceleration" of a sort. That's what the Librarian is doing here.