People are fundamentally different. Someone may really enjoy structure and being told exactly what they have to do. Others want ambiguity and open-ended challenges. Some want stability, some want opportunity. So when you hear someone complain about a company (or praise it, I guess) it's important to ask yourself whether this person's values and interests are similar to yours.
Also keep in mind that people who are crushing it are much less likely to spend time talking about this stuff, while people who are not doing well/miserable have more incentive to vent. So often times it's not just subjective to the person but you're more likely to hear complaining than praise all other things being equal.