If the concept that change cannot turn one species into another species is accurate, then the dilemma of how these new animals came into the picture still remains. Animals that did not exist 300 million years ago exist today. Trying to get around the timeframes by claiming that the world is less than 10,000 years old, falls apart by other sciences, such as astronomy or geology. The cat kind had to exist in the first place in order for a tiger to have changed from it. And the fact is a cat kind was not around at one point. So, something else allowed tigers and all the other cat kinds to exist today when then they did not exist in the past.
Looking at the evolution of motorized vehicles is a good example. Starting with a simple Model T car, you see that basic design expanded into motorcycles, trains, airplanes and rocket ships. Now there is obviously a different component here. Mechanical vehicles cannot reproduce themselves. Animals can. And when you look at animals, you see the same basic design that has expanded into different sizes shapes and abilities.
Are there issues with the theory? There are aspects of evolution that are not full understood yet, no one has ever argued that it is fully understood. However, every year, the information continues to build and develop a better way of understanding the process. As with many scientific ideas, the people who argue against evolution refuse to acknowledge that science is an ever growing body of information. They want to claim that if it cannot be explained today, then it will never be explained. ID relies on a double-standard. While Evolution scientists are expected to explain and predict everything, ID is points out issues and then triumphantly declares that evolution is wrong. When mistakes in ID are pointed out, the proponents of ID simply move to a new area of attack. When Darwin proposed his theory 150 years ago, Darwin didn't know, for example, about the details of DNA. Just as discoveries in physics have made tremendous progress since Newton, biological evolution has come a long way in the past 150 years. But evidence keeps confirming the general model that Darwin proposed (common ancestry, natural selection, etc.)
What people who protest against evolution fail or refuse to grasp, is that it explains the diversity we see today. No other theory can accurately make that claim. And when they say that change occurs, but there is a limit, they need to explain exactly how that limit occurs, which they never do.
Have you ever wonder why creationists sell their theories to the general public rather than trying to get them published in scientific journals? They know that they have zero scientific validity, and any real scientist would see that. "Creation Theory" has no mechanism, therefore it is not a scientific theory. It isn't a question of whether it's a good theory or a bad one. It isn't a question of whether it's better than evolution theory or worse. It's the simple fact that Creation Theory doesnot fit the requirements of a scientific theory at all. From a scientific standpoint, there is no such thing as Creation Theory; the term is simply a misnomer that people have applied to an irrational religious belief.