It's simple actually. You're assuming everything should show massive change. This is wrong. Sometimes changes are tiny and in some cases certain species have effectively "plateaued" - they have nowhere to go within their current environment and will only change if something changes around them.
As for speed, again you've got in wrong assuming 5 million years isn't enough. There are plenty of examples of species evolving faster than that with drastic change.
The pace, and extent, of evolution depends on rate of mutation of genetic material, rate of generational change, plus a whole host of environmental factors.
The bottom line is it is perfectly reasonable for certain species to show very little to no change depending on their environment and what they are.
Evolution only takes place where there is viable, more successful changes to evolve to combined with suitable environmental impetus.
You have to remember you're talking a minority of examples of out millions of clearly evolved and evolving species.
Try to be reasonable... its easier than you think...
