Major manufacturers -- like Intel, AMD or ARM -- have spent years upons years developing methodologies, technologies, micro-architectural optimizations, and testing+development+evaluation infrastructure. This is the key for understanding how to navigate and ensure good performance across the many different trade-off and optimization domains in performant-processor design.

This is not easy to acquire or build. Some is wisdom from decades of design and iteration. Some is hundreds of thousands of engineering hours. Some is big money.

RISC V is a new open source project. Who knows how close they will ever get.