NET 8 has undoubtedly showcased remarkable improvements in performance, and the dedicated efforts of the .NET team have positioned it as one of the most performant programming languages available today.

However, during my review of the benchmark data, I identified certain areas where performance has regressed compared to .NET 6, the last long-term support version. While many of these findings do not exhibit a significant drop in performance, it’s crucial to acknowledge that when using methods demonstrated in this article that are invoked possibly thousands of times per second, the cumulative effect of these performance losses can become substantial.

https://dotnettips.wordpress.com/2023/11/14/analyzing-performance-issues-in-microsoft-net-8/

Мопед не мой, мне что-то недосуг бенчмаркать. А ссылку на репо со своими бенчмарками автор не предоставил.