It's fine to grumble about testing, but the debate is not about the tests.
Teachers performance in the US has been terrible for many years. Partly this is because of bad management, partly because of low pay, and partly because of teacher unions preventing any action against the worst teachers and insistance on tenure tracks.
The reason testing is good isn't because it is somehow super accurate. It is good because it keeps teachers honest. Without testing, how do you measure teacher performance at all? How can you tell if someone who is capable of teaching well isn't just being lazy or getting distracted?
So, if you aren't a fan of testing as a way to measure and improve teacher effectiveness, please find an alternative that works better. Just not having any metric at all is far worse than the imperfect tests we have.
It's easy to point out problems. It's useful and important that people find flaws and fault. In this case, however, just pointing out the deficiencies in standardized testing doesn't help anyone unless it either leads to a more effective alternative, or improvements in standardized testing. Standardized tests might be very imperfect at measuring teacher performance, but it's far better to use the tool we have than to just throw up our arms and assume that all teachers are equally competent.