There were some teething problems with Windows 11, and now that it has been out for a while, there are still fresh bugs being discovered. Alternately, ancient concerns that have been given new life. Since you upgraded to Windows 10, how fast is your SSD? The random performance of some NVMe SSDs has dropped dramatically, according to several users.
When this happens, the random write speed can be anywhere from 2x to 4x slower than it was prior to the upgrade. Multiple manufacturers appear to be affected by this, thus it doesn't appear to be a problem with one particular drive.
Some people's random reading speeds have also decreased. A second SSD in the same machine appears to be unaffected by the issue, despite the fact that Windows 11 is installed on the first one. Sequential read and write speeds, on the other hand, are largely unaffected — and can actually get better.
This problem wasn't just discovered recently; Reddit threads about it date back at least three months (while W11 was still in beta). In one of them, a Microsoft official stated that the team is aware of the problem and examining its root cause. But that was three months ago, so it's not like it's still relevant. Since a few days ago, no solution has been found in the topic. Microsoft's forums have a similar discussion going on as well.