When KC came in September 2018 we had 7 points from 10 games. Taking over DA's jigsaw he immediately turned the season around and from the remaining 36 games achieved 54 points ( equivalent to 69 points over a full season).
Since JB has taken over KC's jigsaw the uptick in results has been miniscule, KC had 24 points from 26 games and JB has 16 points from 15 games (equivalent to 49 points over a full season) so still relegation form.
Personally I like the fact we have 3 ntfc men in charge but it is a results business and the product on show has not been good. If there is no suitable experienced manager available it may be worth taking a punt on an up and coming manager from the National League or a younger man employed as a number 2 at another club.
I agree with your conclusion but let's not forget when KC came in we were in league 2 and now under Brady we're in a much harder league 1.