Why is playing games 'not useful'?
- why, sure, if you can find somebody to pay you money so that you can play games then it's useful to that somebody. Unless they are *forced* to pay you money for playing games, then it's not useful, it's useless and worse, it's oppressive.
By participating in consumption and consumption only and by not producing while consuming, your life is not in any way helpful to those, who are producing whatever you are consuming.
Let's make it easy for you: 100 people on an island. 10 are producing every single thing needed for the 100 to survive. Unless the 90 are providing sexual or other types of favours, they are not producing anything of any value to provide the 10 with a meaningful exchange for their production.
However if the 90 gang up against the 10 and the 10 do not have enough weapons to take out the 90 without dying themselves, the 90 can force the 10 to be the slaves of the 90.
The 90 then would be eating, drinking, living in houses, using energy and every resource and good produced by the 10.
You can say: without the 90, the 10 would have nothing to do. Of-course that's pure nonsense. Without the 90 the 10 would have more leasure and less worries as they only have to produce for the 10. The 90 are adding nothing except for the effort that needs to go into feeding the 90.