Question for Creationists?

You cannot deny that animals adapt. That's been proven through domestication, bacteria gaining immunities to antibiotics and the pepper moth incident, among countless others things. I understand the argument that adaptation does not automatically equal evolution, but, my question is: then what else would happen with these minor adaptations over millions of years if the world gradually, but drastically changed? Yes, I understand that the world is, according to The Bible only a couple thousand years old, but, as I understand, Creationist thinking isn't that evolution hasn't happened because not enough time has ped, it's that God's creation is immutable and new species would appear under no cirstances. So, as long as your responses aren't just quoted Bible verses or rants about how I'm going to Hell (because I get those far too often), I'm seriously interested in hearing your thoughts as to why these adaptations would not, over all that time, add up and change a species.