I certainly don't want to give the impression that I know everything very well, including genetics. No matter how well you do your best to breed responsibly, you will never stop learning and you will always be faced with surprises.
However, what I have come across regularly lately, should in my opinion, be questioned. If in one family tree, with 30 ancestors on it, there are several times 10 different bloodlines, then I wonder what those breeders are looking for.
Even if you are a "line breeder", you will have to regular bring in an "outcross" to correct certain mistakes or for blood changes. Then look for a partner who does not have this fault and does not inherit it. Then you must go back to your own line and see that you achieved what you were hoping for. By repeating “outcross” on “outcross” over and over, you will certainly not get any further.
It is also very important to recognize the mistakes in your own dogs and to act accordingly. In the past you could often tell who the breeder was just by looking at the dog. The dog had certain characteristics that were special to that kennel. You almost don't see that anymore.
Breeding should always be something more than putting two dogs together and seeing what happens. To build your own line you will have to work on it, by thinking things through and selecting. Also consider beforehand: what can I do with the puppies to progress?
Many hundreds of books have been written on this subject, but no one has ever been able to breed a dog that is perfect in every way. There is always something to criticize and that might be a good thing.