Bhagavad Gita, Chapter 8, Verse 11

What the knowers of the Veda speak of as Imperishable, what the self-controlled, freed from attachment, enter, and to gain which goal they live the life of a Brahmachârin, that I shall declare unto you in brief.

Real, serious paths already exist toward this, and Krishna is about to describe one of them concretely.

This acknowledges genuine precedent, real traditions have pursued this goal through real discipline. Krishna doesn't dismiss that, he's about to add his own concrete description of the actual path.