But there was this difference: that such knights carried with them some substantial recommendation, either numerous retainers well armed and accustomed to battle, considerable treasure, or at least a reputation for prowess in the field.

Felix had nothing to offer, and for nothing nothing is given.
The world does not recognise intrinsic worth, or potential genius.
Genius must accomplish some solid result before it is applauded and received.

The unknown architect may say: "I have a design in my mind for an impregnable castle." But the world cannot see or appreciate the mere design.

If by any personal sacrifice of time, dignity, or self-respect the architect, after long years, can persuade someone to permit him to build the castle, to put his design into solid stone which squadrons may knock their heads against in vain, then he is acknowledged.

There is then a tangible result.
Felix was in the position of the architect.