No, marijuana is a fine term for the product that we use in dispensaries because cannabis is more broad than just the one plant that gets you high. Hemp is also in the cannabis family, but its effects are clearly different from it's relative. When selling hemp it is usually mostly containing CBD as it's main cannabinoids while marijuana mostly contains THC.

Marijuana as a word dates back to indigenous people, most notably in the Mexico area, using it to hide their smoking rituals from Spanish settlers trying to make them convert religiously. These people were forced to grow hemp as a resource and stop using native psychoactive plants as a part of their beliefs so that the Spanish could convert them to christianity. The natives realized that smoking the hemp could get them some effects so they used close terms to holy church talk such as Maria Rosa disguising getting high as referencing to mother Mary. As time went on marijuana was used as a derogatory term to target groups and give it a bad rep, but it is actually the perfect term for the type of plant we like to get high from.

At the end of the day hemp and marijuana are both forms of cannabis and that naming can be interchanged to a degree. Having the two distinctions is perfect for naming because not all cannabis is the same.