While the power of PCR isn't in question, I think you're overstating the case at bit. It didn't "nuke" whole areas of Biology, but it did add clarity and it did answer questions which previously were hard or impossible to answer using other techniques.

I think you're being somewhat unfair about taxonomy. Before whole-organism sequencing, classifying based upon detailed physical characteristics was the only option available, and for the most part that classification did match the genetic data. Sequencing did correct some mistakes, of course, but I think it does a disservice to all the people who did highly-detailed and rigorous work in that field to claim it was "nuked" when that simply is not the case. PCR-based sequencing did not invalidate most of our existing knowledge, but it did make it a quantitative science rather than qualitative.

Consider also that PCR also brought with it a number of problems of its own. Classification based upon sequencing of individual genes also led to mistakes because it didn't account for xenologues or independent evolution of the same mutation. These were later corrected with the advent of whole-genome sequencing and comparison of multiple genes. It also led to a lot of research published demonstrating that the presence of certain genes or expression products correlated with certain outcomes. And a huge amount of that was completely false, because they failed to investigate the downstream effect of these differences. In too many cases, there wasn't any functional effect, or the wrong conclusion was drawn because of experimental error and bad statistics. The bar for publishing in a good journal is now much higher, but it's still all to easy to misinterpret genetic data.

You're definitely overstating the case. I don't forget about this stuff, since I was getitng my undergrad, grad, phd and postdoctoral work in this field.