This may be a bit of a subjective question, so I'm not sure if this is the best place to ask this... but I'm working with a client that wants a completely custom Wordpress site, and I'm very used to developing themes from scratch or using _s to just get the basics in there and ripping out everything I don't need. I'm not a big fan of using plugins and widgets if it's something I can build myself (also to avoid code bloat).
With that being said, the client is pretty set on using Genesis framework, and I'm trying to find resources as to what Genesis brings to the table that can't be accomplished outside of Genesis - specifically for a custom built site, as opposed to using an established, pre-built Genesis child theme. It seems like an unnecessary route to go if everything is custom, but I didn't know if maybe I'm missing something.
There is nothing that Genesis theme does that cannot be replicated with custom built theme. After all Genesis is just a theme.
Genesis theme has tons of feature which you can look into by going to its site, but I use that theme if I have to prototype a wordpress site in very short amount of time. Using its different widgets and layouts, I can build a different looking website in few hours.