Fact: Anyone can sit with a user and ask the user to carry out some tasks on a product. So, in principle, anyone can do usability testing.
But: Quality usability testing that delivers reliable results is different. Quality usability testing requires skills like empathy and curiosity. It requires profound knowledge of recruiting, creating good test tasks, moderating test sessions, coming up with great recommendations for solving usability problems, communicating test results well, and more. The CUE studies have shown that not every usability professional masters these skills.
We need to focus more on quality in usability testing.