On the Online Self-Editing Course which I'm running jointly with Debi Alper, my tutorial was talking about characterisation, and I said that at the self-editing stage you need to ask yourself whether your characters are too off-the-peg. "Off-the-peg" is a term I owe to Susannah Rickards, originally for the kind of language which does the basic job perfectly well (and its "rightness" can seduce new writers into feeling it's really right) but is never really fresh. It sits somewhere between the fictioneers' "second-hand" and the poets' "received language", as a way of describing something which we've read or encountered many times before, although it hasn't yet degenerated into a confirmed cliché.
Are your bus drivers men, your nurses women, your teenagers sulky, your middle-aged mothers kindly? Do your Frenchwomen dress exquisitely and your Germans have no sense of humour and your elderly men wear cardigans? Of course we all fit some stereotypes of our age, gender, class, nationality and so on, but we all run counter to others. Off-the-peg characters, like off-the-peg language and off-the-peg plots, are the easiest for the reader to take on board, because the meaning is ready-made. The reader's mind slides straight over and moves on, because there's nothing new or different or surprising about the ideas, no individuality about characters who fit all our preconceptions, nothing about the arrangement of words which makes them come alive, no desirable difficulty to mean readers make the story their own. As a writer, it you're going to find all those newnesses/differentnesses you have to learn to stop your own mind slidling briskly over what you see or think: you have to push your observing and your imagining to the limit. And then you have to push your willingness to go beyond the usual ways of writing these things, to the new or different ways: to the limit. Only when things are really new, or familiar things are presented in a new light in new combinations, will we really experience this character (this story, this setting) as an individual: something as unique and potentially surprising as any other human being.
The risk of off-the-pegness is also higher with secondary characters, since you can't spend too much story-space on them. And sure, with really minor characters you don't have to round them out to full main-character complexity and detail. But it's still important to challenge your defaults and stereotypes, characters still need to come alive, and by even more economical means.
Of course your story may be built round the challenges of being someone surprising in a job or a world: P D James even called one of her novels An Unsuitable Job for a Woman, and Elizabeth Jane Howard wrote a whole novel about a straight male hairdresser, and his straightness was part of the story. Even if it's not built like that you won't, in the interests of realism, be able to avoid dealing with it, and you may choose to avoid that by not inverting a stereotype. But with minor characters, why not? Well, if the novel makes a great song-and-dance of it - characters noticing and commenting on the female priest, the male nanny, or whatever - then there is a risk that some readers feel it's mere PCness or bolted-on for a cheap sensation, as it were. Others will positively enjoy how the story doesn't play to stereotypes. But if the story doesn't make a song and dance of it then many readers won't feel PC-bashed in the least; it will just add individuality and therefore vividness to the story. After all, a less off-the-peg phrase for a sunset, for example, won't get the vast majority of readers thinking like a bad Ealing Studios Cockney, "Ooooh, 'ark at 'er, avoiding clichés!": it's only over-aware readers like us who'll do that. Most readers will just see and and believe in the bus journey or the sunset more, and more vividly. Similarly with minor characters.
So I'd suggest developing a reflex of challenging your stereotypes; it's good for your writing in general to get into the habit of reversing your defaults, and checking if things wouldn't be better and more interesting that way round. You may well to decide to go with the more traditional male priests, black DJs or whatever, and that's okay. There are plenty of both, after all. But in the end, what readers are looking for in a novel is something which - using language, ideas, characters, situations - finds a newness in the ordinary world, a world new to them, in a way which makes them believe in it. And to do that you do have to keep checking how your writing uses or refuses to use the defaults of your world-view - you have to keep your off-the-peg alert turned up high - because the more ordinary your stuff is, the less readers will actually read it.