Workflow is slow, tedious and not streamlined at all. It wasn't revised for maybe a decade and it shows. That's all. Time is money, and LR is lacking a fast workflow.
In your personal opinion, however tens of thousands of professional users would disagree with you, there is very little you can't automate and if you use consoles rather than keyboards it can be incredibly quick. I've seen wedding studio pros shuttle through 10,000's of images a day each inspected, graded, culled, straightened, cropped, custom develop settings applied and keywords applied. If you can't do it fast it isn't the softwares fault.
I am a much more modest and probably more typical user, my Library is 100,000 images and everything is pretty much instant, but I took the time to optimize my Library setup and I use fast connections for RAW files and an internal SSD for Smart Previews. I can scroll through images, jump from one folder to another and pull up the Develop module and work if the RAW files are connected or not, and all with zero lag.