The door-keeper may well be seen as a lowly job - but it is also a very responsible job - not just anyone can perform this task.
Jesus is known as the door or gate. The door to where?
Therefore Jesus again said to them, "Truly, truly, I say to you, I am the door of the sheep. John 10:7
I am the door. If anyone enters in by Me, he will be saved, and will go in and will go out and will find pasture. John 10:9
They go in to find good food, a safe place without fear. Food = truth and no fear = love.
The Door-keeper does not let wolves in, only the sheep, only those God has chosen.
Open to me the gates of righteousness; I will go through them, And I will praise the LORD. Ps 118:19
The Psalmist is often writing about the coming Saviour - here he looks forward to the grand opening of the Kingdom of God to the righteous - the righteous made so by the Saviour. The only place of God's righteousness is His kingdom and Jesus is the only way into it. It has been modelled by the tabernacle, the temple with the offerings and sacrifices - and now fulfilled in Jesus and his sacrifice who has opened up the holy place for all to enter (at their appointed time).
We might also note,
Everyone the Father gives me will come to me, and the one who comes to me I will never drive away. John 6:37
Jesus role is to keep out the wicked (sheep and goats parable) - keeping the chosen and casting out the others. Jesus, as mediator and judge knows the difference, but also knows that all can be found in him eventually.
Of course, Jesus came as a lowly servant. Serving God and man, but he has qualified to become the one at God's right hand. Yet he is still the only way to the Father - still the door-keeper at the best address in the universe!