Precambrian fossils have been know since the 1880s and earlier. There were certainly multicellular animals before the Cambrian explosion, but they lack hard skeletons and don't fossilize well. It's as if all organisms were single cells or marine slugs with no hard parts. There are fewer fossils from that period, but they definitely exist. Just not in as great numbers as those that come later. And of course since the Earth's crust erodes all the time, there are far, far more rocks that are 200 million years old than are 2000 million years old.
The Cambrian represents a major diversification and the appearance of both inside skeletons like ours and outside skeletons like those of insects and lobsters. Diversification is a common theme in Evolutionary biology. The diversification of marsupials in Australia is a smaller but equally interesting example. Diversification is where species come from, so it's not at odds with macroevolution, but, on the contrary, the very essence of it.
Fossils are not a red herring. They are the backbone (no pun intended) of all that we know of the history of life on Earth. All that molecular biology has done is to provide confirmation for 90% of what we already knew and minor adjustments to the other 10%. (I'm using these numbers only approximately.)
Molecular biology was like an independent witness coming into a criminal trial and confirming the statements of four earlier witnesses--first paleontology, then comparative anatomy of living species, then comparative embryology, and not least, biogeography--the distribution of both living organisms and extinct ones. All these earlier witnesses told the same basic story, although from different perspectives. Molecular biology confirmed their stories.
The fact of evolution comes from the fossil record. HOW evolution happened, the details of mechanism, are better sorted out by looking at genetics on the one hand and ecology--the furnace of selection--on the other.
