The word has meaning because we all agree it has meaning.
Corporations exist because we all agree that corporations exist.
Money has value because we all agree that it has value.
The United States of America exists because we all agree that it exists.
Yes, there is a difference between objective reality and intersubjective reality. But I think you're making too much of that difference.
A huge amount of our everyday world is based entirely off broad mass agreement. The vast majority of the things we interact with in modern life would immediately cease to exist if all the people who believed in them just vanished one day - if an extraterrestrial species arrived on Earth the day after, they would not be able to observe almost anything about our lives. That doesn't mean our reality is fake or that our interaction with it is arbitrary. It just means that it is geopolitically and/or culturally defined.
Bottom line: Yes, social science is hard, but lighten up.