Part of the problem is that the standard to say something is "good" can vary wildly, and often does end up becoming quite low. See inflation of grades, video ga

Part of the problem is that the standard to say something is "good" can vary wildly, and often does end up becoming quite low. See inflation of grades, video game reviews, Yelp ratings, etc. If I see a 3 star restaurant I'm highly skeptical of it, even though 3 stars should be considered perfectly acceptable by intended definition. On Google performance reviews scores could range from 1 to 5, with 2 being "meets expectations". A 2/5 sounds pretty bad, but the description sounds like the person is doing their job fine and is not an impostor. So what does it actually mean? But that depends from manager to manager anyway. IME many of them end up inflating and "exceeds expectations" loses meaning. Point being, I think you need a lot more context to determine what "good job" actually means. If feedback is sufficiently detailed you can make a pretty good estimate right off the bat, but unfortunately people are bad at giving feedback in general. So especially when new to a team and you don't have any priors for how they use language, it makes sense to have some doubts. I'm sure this can become pathological, but is the unhealthy version actually as prevalent as all the talk about impostor syndrome?