To me, this is a lesson and reminder to wait on the Lord and not move in our own efforts when circumstances appear dark or tough. Notice, once Jesus was involved again, they immediately got to where they needed to go.
The same people who were just physically fed, nourished and looked after, wanted more. They wanted more miracles and seemingly were looking more to the miracles they physically benefited from, rather than to the One performing the miracles that could nourish and feed their souls. It appears they were unable to move beyond their senses and the empirical nature of what God was doing, into the spiritual relationship and understanding of what Jesus was communicating. He was encouraging them to see He was the bread of life. His Words, given by the Holy Spirit, were to sustain their souls forever. However, their very literal interpretation caused them to turn and walk away. This compels me to pray our eyes are always spiritually open to what God is doing, rather than blinded by what we think we see, which could cause us to turn from Him.
There seems to also be a lesson on asking the Lord to cause us to see, accept, be thankful for, and give to others from the Spirit, rather than solely operating in the flesh or our own efforts.