What one should be looking for are guideposts based on experience. Over time, if you read what a person writes, you'll develop a sense of whether you are more or less likely to have the same reaction to a show. This is true whether it is a professional critic or someone here. That sense can also be further refined over time. Thus, I might find that my taste aligns with someone for musicals but not plays, for drama but not comedies, for classical but not contemporary, etc. This is a healthy thing and it is enhanced nowadays because we have such an abundance of opinions expressed and accessible to us. What you DON'T want to do is read something from an unknown source and treat it like the gospel. (Imagine, for example, if someone came here and read but one opinion on a show and unluckily it had been written by After Eight!)