1. homology - even though professed by Darwin and given as one of the strongest proofs of evolution by him, it is no longer essential because it was easily disproven. There are far too many easily seen examples of similar traits in totally unrelated species. So, to fit the facts more accurately (and make sure that evolution cannot be refuted scientifically) now either divergence or convergence is proof of evolution.
2. fitness - since the biological creation of new genes cannot be shown by mere fitness (fitness does not operate until a gene has been perfected), evolutionists threw away fitness and postulated neutral drift. However, since fitness is still required for some of their arguments (such as why do species evolve in the first place) they have kept both arguments in their arsenal of excuses. Either fitness or unfitness is now proof of evolution.
3. gradual evolution - since the fossil record does not show gradual gradations between classes, then gradual evolution cannot be true either, hence punk-eek or the intermediate species were on vacation in Hawaii and left no fossil record of the change was developed. While this 'magical' excuse for the lack of evidence in the fossil record requires no other explanation, the evolutionists still hold to both theories and only use punctuated equilibrium when lack of gradualism is used against them.
As the above shows these 'evolutionary' modifications make the theory of evolution much more 'robust'. It allows evolutionists to take both sides of every question and say that everything that occurs is due to evolution. Of course, since it also makes evolution completely illogical and completely non-falsifiable, it also turns it into an ideology instead of a scientific theory.