Same here....
8‑core 9th‑generation Intel Core i9
64GB 2666MHz DDR4 memory
AMD Radeon Pro 5600M with 8GB of HBM2 memory
1TB SSD storage
16-inch Retina display with True Tone
i have the highest specs Mac Book Pro 16 with the highest modifications, and after i upgraded the OS to macOS Big Sur, my laptop become super slow, like it takes a second to open any random file, like images or text files.
i feel so disappointed of the new upgrade.