So what I mean is that, to me, a real gallery type site would allow you to do things like filter down by tags and explore specific types of posts by an artist that catches your attention, with combinations of filters, etc. (This would obviously depend on how they used tagging as well.) pixelfed is also built around adding pictures as posts.
There are third party clients that can present information different ways, but the actual website is how you'd generally expose people to your content (especially because it's not something massively popular like instagram). It also, while good at what it is, just doesn't provide the kind of control over structure and organization that I personally would prefer to share my pictures with, which is why I haven't managed to bring myself to add my pictures in bulk there.
But like I said, it's good at what it is and may fit his needs better than mine, so it's worth a good look.