Everything that's enjoyable in life can meet that definition. For practical purposes, we only consider severe cases to be addiction, but it's not well-defined. The article you linked says:
> However, there is no agreement on the exact definition of addiction in medicine. Indeed, Volkow et al. (2016) report that the DSM-5 defines addictions as the most severe degree of the addictive disorders, due to pervasive/excessive substance-use or behavioural compulsions/impulses. It is a definition that many scientific papers and reports use.
> The DSM-5 and ICD-10 only recognize gambling addictions as behavioral addictions
I don't think the DSM-5 has any principled reason for recognizing gambling addictions but not video game addiction or shopping addiction, other than gambling addiction being particularly harmful.
Whether social media is beneficial or causing substantial harm is not well defined or easily measured. It's a subjective thing that will be debated and rely on judgement.
That's part of why it can be contentious; people can declare themselves addicted but one suspects they sometimes do it to avert blame for some related action.
And whilst many things in life can have this property and need to such that we get enjoyment out of particular aspects of life.
There are particular things which short circuit reward pathways to a greater degree. Such as drugs, alcohol, gambling, video games, smartphone addiction.
Smart phone/video games are designed to constantly reward us as much as possible
Wikipedia has a better definition right at the top than I can offer: https://en.m.wikipedia.org/wiki/Addiction
The crucial point is it is characterised by neurological changes that lead to short circuited reward pathways. The idea of addiction to social media a perfectly consistent with its action and moreover, consistent with the notion that its effect can be enhanced by design.