Isaiah 5 and John 15 are both about the Lord’s precious Vine. Note the difference. Jewish people being addressed in each, and they are probably made of the same stuff, capable of the same stumbling.
But in the first citation the subjects are otherwise occupied. God’s blessings are slighted. The truth side-lined, and doom resulting. Note the 6 woes.
In the second citation the subjects are told point blank that they must abide, must cling. Apart from the life connection with their Master Jesus they can do NOTHING. Remember that, simply thankful beggars holding on for dear life. And the results are joy, peace, and the love that obeys.
Clearly the treatment of God’s word is focal in each message. See Isaiah 5: 24 and John 15:7.