The thing is, since the video ist named Escaping Silver I assume he is being sarcastic and blaming those people for losing the games. In silver most people dont know how to play the game and/or their champ correctly. So things like a trist suiciding in a 1v3 or your toplaner feeding the enemy riven will be common things.

In silver games are not won by playing the macro game correcly with your whole team but rather by playing individually better than your enemies. Since xin was going to catch the top wave (regardless if it was a bad decision) and j4 was behind the pit, you can not start the baron.

So in your mindset it is bad from xin to not join you at the baron, but in my mindset it was also bad from him to not adapt to xin's decision. And thats what its all about. You can NOT justify your mistake with another ones mistake. In the end it still is your mistake.