I agree with your opinion. If a person does not know bitcoin then he should not invest in it. The value of bitcoin is not stable, if you do not have enough knowledge about bitcoin then you will be scared whenever its price drops.
This not only applicable to bitcoin but for all types of investment, before investing we should know the basics of the bitcoin, how it works and all then can invest in it, without knowing anything it is not good to involve, better know the elementary about the bitcoin and then invest.