When evaluating scientific research portals, the most important factor is the entity behind the domain. Because usdf-rsp.slac.stanford.edu is a subdomain of Stanford University and represents the Rubin Observatory's data project, its legitimacy is clear. This is not a commercial service or a typical website, but a specialized utility for researchers to access data. You should expect a functional, utility-focused interface rather than the polished experience of a consumer website.
Since this is an institutional project, you will not find typical customer support features or legal disclosures. If you are wondering if usdf-rsp.slac.stanford.edu is a scam, the answer is no. It is an official tool for the Legacy Survey of Space and Time. While the site load times are sometimes sluggish, this is common for specialized research infrastructure hosting large datasets. Your interaction here should be strictly limited to the intended research and data analysis tasks. There are no consumer risks to consider, as the platform does not handle personal financial transactions or commercial services.