

The start menu being React Native is irrelevant. If it were React in an Edge web view that would be a different story.
Opening the start menu should cause a spike in CPU usage. You want the CPU to open the menu ASAP instead of dragging out the process so the CPU usage is more flat.
But everything in Windows these days is wasting time stealing your data, loading ads or other unnecessary data from cloud services, and interacting with “AI.” Performance is one of the lowest priorities, somewhere between software quality and privacy. Since mid Windows 10, Microsoft consistently replaces things with modernized, but worse, versions and never returns to finish making the new version as good as the previous version that evolved over decades. It’s a really expensive way to ruin a product. They could make a React Native start menu where people wouldn’t complain about the performance. They probably did and people are only noticing now because of a recent regression.
vdo.ninja?