The meaning is:

Non-doctors can't/couldn't/can never understand that.

Also, I'm pretty sure that this is a misprint. They probably intended to use the prefix “не-” and not the particle “не”. I would write that sentence as:

Неврачам этого не понять.

EDIT: Here is an article about the “не-” prefix, which has “неврачи”, as well as other examples like:

(…) нефранцузы, немарксисты, нехристиане, неспециалисты, немосквичи, нерусские, недемократы, непоэты, нетермины, неметаллы, нестихи; (…)

The meaning is:

Non-doctors can't/couldn't/can never understand that.

Also, I'm pretty sure that this is a misprint. They probably intended to use the prefix “не-” and not the particle “не”. I would write that sentence as:

Неврачам этого не понять.

EDIT: Here is an article about the “не-” prefix, which has “неврачи”, as well as other examples like:

(…) нефранцузы, немарксисты, нехристиане, неспециалисты, немосквичи, нерусские, недемократы, непоэты, нетермины, неметаллы, нестихи; (…)