Can you think of reasons why more complex organisms cannot give rise to new individuals through regeneration?

Complex multicellular organisms have highly differentiated tissues made by specialised cells and tissue combinedly makes organs and then collectively an organ system is formed by organs. So this says that a single cell of a tissue is not able to reproduce another type of tissue in complex multicellular organisms. For example, a dog is a complex multicellular organism and if we cut the dog into two parts, then the cells of one part won’t be able to reproduce cells of the other part to produce a complete dog .