This is a good article about “folding” – compacting your stories down by making every element do more work and connect more closely with the other elements. Rather than have two colourless minor characters, combine them into one more interesting one.
There’s a caveat to this, as to all writing advice. Pushed too far, you can end up with unlikely coincidences about who knows each other, and the reader can get the feeling – as I did from Dracula – that the population of Great Britain is approximately 12 people, given how many coincidental connections there are between them.