It’s important to note that the “true tempo of early animal evolution” exists in evolutionists’ imaginations, not in the rocks.
If this is the best answer evolutionists can come up with, it’s game over for Darwinism.
Recently, a team of British paleontologists added a new pseudo-explanation.
If you ever encounter a horseshoe crab on the beach, you are a looking at a creature that would not have appeared out of place hundreds of millions of years ago.
In a physical world there will be design constraints, so it is only realistic to expect tradeoffs.