I'm not sure exactly what you mean, but the primary way of adding items to Zotero is with the Zotero Connector browser extension, which lets you save high-quality metadata and PDFs with a single click from a huge variety of sources (certainly including humanities sources, since Zotero was created by historians). No other tool comes close to Zotero's abilities here. Metadata quality does vary by site, though — Google Scholar specifically only provides limited metadata, so you'll often get better results by clicking through to the linked article and saving from there. We have plans for functionality to flesh out incomplete metadata retrieved from subpar sources.
Zotero can also automatically retrieve metadata from PDFs you drag in, which should work for the vast majority of recent PDFs and many older ones with DOIs assigned, though that's not meant to be the primary workflow.
> documentation for things that would be useful like hooking up to academic library proxies is nonexistent
Current proxy documentation is here [1], and that's what's linked from the main documentation page. I've fixed the outdated page you pointed to — thanks.
Note, though, that the proxy functionality is meant to work automatically for the popular academic proxies, so most people don't need to configure anything to use it. (And as far as I know other competing tools don't offer anything like this.)
> no better bibtex for zotero 5
BBT has worked with Zotero 5 since last year.
Disclosure: Zotero developer
[1] https://www.zotero.org/support/connector_preferences#proxies...