Getting our definitions straight is essential to sorting this out and preventing us from talking past one another. We can’t tell to what extent we agree or disagree without it.
For example “Descent with modification” is one definition of evolution, I guess a preferred one. To me it could also be a form of creationism or at least intelligent design, depending on how the "modifications" occur. For example, farmers breed animals for certain traits and get them through descent with modification. They select far more powerfully for desired traits than nature does. So that fits this definition of evolution, but surely it is intelligent design as well.
Let’s have a thought experiment: Now suppose instead of farmers who went around selecting for traits, God Himself did so. If a certain group got a rare mutation that would produce a benefit if paired with another rare mutation which existed only in a second isolated group He would know it and be able to put those two populations together so that they would have the suite of mutations that, when combined with yet another rare mutation four generations from now, would result in a new function. So He is using Divine knowledge to leverage natural processes to produce something new. I would say that is evolution (descent through modification), intelligent design (intent drives the changes not natural selection) and “soft-touch” creationism (He intervened in the natural world to produce outcomes even if He never touched the genomes directly, He merely guided natural events in a way that nature would not in herself at anything like the same rate).
Now suppose that instead of taking the role of a selective breeder (with perfect knowledge) only, He also assumed the role of Genetic Engineer. That is, instead of strictly waiting for Nature to come up with mutations which could be combined to create new function, He did just what our engineers do. He made cuts and inserts in genetic code. Maybe nature would never get a particular protein to fold just right waiting for chance or mutation so He inserted a gene which would. So when our scientists make mice which glow because jellyfish genes have been inserted in them, and this population breeds, is this “descent with modification”? Well maybe, but the modification did not come wholly by "natural" descent. It is doubtless intelligent design and special creation, and questionably evolution as well.
That said, such a situation could still involve natural descent, but that would not be where the key modification would come from. Take the gap between a fish and an amphibian. What if over the course of thirty or forty generations God acted to put just enough changes in each generation that they would still be able to be birthed and bred by natural means but each generation would also be further toward the amphibian end of things? This so that even though no amphibian was created out of thin air, or clay, one still had a very different creature though only forty generations removed from the fish. That result would be due to genetic engineering moving things a bit further along each generation. That is “descent with modification” but the modification that matters is via genetic engineering. So is that evolution, special creation and intelligent design all rolled up into one?
Is there really any scientific evidence that known evolutionary processes can operate at the rate and scale necessary to explain all of the "modification" of life on earth through its history? Another way to ask it would be like this, suppose there were a billion earth-like planets and a single celled organism was placed on each. How many of them, using only known biological processes without any intelligent intervention, would have a biotic phase which looks anything like the history of life on earth? I think the number would be "zero". Someone else might think the answer would be in the thousands or even millions, but none of us have done the experiment or anything like it to say for sure. Therefore neither side has a scientific basis for saying either way, though one might have naturalistic assumptions on the question. It is a pity so few can even recognize that there is a difference between the two.
Like Jon Garvey, I don’t think “natural selection” or any of the natural means we have discovered could have, on its own, produced the vast diversity we see today or in the fossil record. I think nature had help. And I think some of this arguing we are doing over it is because we are talking past one another on terms.