Yes, TV shows can be made to be "addicting" but what is the potential harm? Someone sits around watching too much TV? That's not a very big drain on society at the end of the day. Sure it's not great, but the negative outcomes for the society as a whole don't seem to be too impactful.
Now look at gambling. It's certainly addictive because of various techniques used by casinos to get people hooked. It seems that much of society agrees that it also has some negative impact on society as a whole. It drags people into impossible debts which can have a variety of negative externalities... loan sharks, violence, evaporation of wealth, financial crimes, etc.
It seems clear to me that not only is social media addictive but it is also having a net-negative impact on society and that is why people are concerned. If the impact was just people are spending their evenings glued to the screen but not going out and causing societal issues then I don't think anyone would be too concerned.