I definitely don't have a degree in pharmacology and I agree that it would be generally useful in conversations like this which are quite complex.
The reason I mentioned the lack of labels is because in addition to binding affinity (strength of attraction between a drug and the receptor it targets) drug efficacy (strength of the reaction a drug causes after binding to a receptor) is also important.
It is possible to have a drug with great affinity but poor efficacy, or great efficacy but poor affinity, and that particular chart tells tells us nothing about the efficacy of those specific drugs.