Any attempt to review performance that just looks at core utilisation, is pointless. Real performance depends on CPU utilisation, memory management, storage access, and application efficiency and all of that can be affected by whatever else the user has running or is doing with their system at the time.
Anyone who has used Lr for any length of time has encountered situations in which the performance drops, and situations in which the performance reaches unacceptable levels. It happens. Adobe recently (middle of last year-ish) focussed on addressing this. Basically, the functionality had been prioritised over performance in the real world. Improvements have already been made, and I expect there will be more. Anyone claiming it's overall poor is either using absurd, artificial benchmarks, or has a highly convoluted workflow, or has a poorly setup system, or a very low spec system, or they're just jumping on a bandwagon and don't have any real experience).
What counts is how it performs in a real world workflow that is itself reasonably optimised (convoluted workflows are their own worst enemy).