It is possible to transfer traits (we can do that) but genomes contain a great deal of error checking and redundancy, and proteins work together in a complex ‘cellular ecosystem’ where small variations can produce catastrophic consequences to the organism’s ability to survive. So to say we can cumulatively transfer traits between our species is probably true. But all attempts to cause inter-breeding have failed. (Yes, scientists, particularly one russian, have tried it.)
So trait-addition and modification is probably not only possible but may be beneficial (so that we can live in harmony with large mammals in particular by pedomorphic/neotenic evolution as we have done with dogs.) But inbreeding is too ‘primitive’ a method because in all but outlying cases, the genomes would consider the ovum ‘defective’.