Google understands the URL structures of directories. There likely isn't a difference in using hyphens or backslashes in terms of URL keywords.
For instance
www.example.com/photographs/wildlife/
and
www.example.com/photographs-wildlife/
are probably the same thing to Google, both have the keyword
"Photograph Wildlife"
But let's say you were to use the URL www.example.com/wildlife-photographs/ instead. Your URL keyword is now "Wildlife Photographs" instead of "Photographs Wildlife", and this is probably going to be an exact match keyword for a lot more searches.
The clean directory URLs do look better, but the second example gives you more of an exact match for what people are searching for. As a result, you may prefer to structure your site to be closer to the search terms you are targeting.
The following structure probably yields the same targeting results. Though if you don't actually have a "wildlife" category, because your category is actually "photographs", you may prefer to use the hyphenated version.
www.example.com/wildlife/photographs
www.example.com/wildlife-photographs
The exact match could make a modest impact, but as long as your page is targeting your keywords, Google should understand what your page is about. So if this exact match version requires your entire site to be restructured to accommodate it, it may be a better investment of your time to work on other improvements. The URL structure may be impactful, but not necessarily a massive different in signal. Ultimately, I would prefer to have the exact match URL if possible.
If the choice is between www.example.com/photography/wildlife-photography/ and www.example.com/photography/wildlife, then I do think the first is rather redundant, and I would prefer the second structure.
If you made the URL www.example.com/photography/wildlife-photographs/ then at least this is slightly less redundant and you're targeting multiple versions of the same keyword.
It's also reasonable to have photography/wildlife-photographs/because it shows me that the page likely has photographs on it. Whereas photography/wildlife could be an article about photographers and doesn't necessarily indicate that the page is going to be full of photographs.
