Talking about dashboard load-in times is straying off-topic a bit, but it is related too.
AFAIK, the dashboard pulls in data after some time of cache expiry. For example, a version check, checking for problems, and a lot of database queries.
One approach might be to more aggressively display cached data until explicitly requested. Or maybe have data in collapsed sections that don’t pull up fresh data until the section is expanded. In other words, fresh data on demand.
Personally, I’ve always looked at this as a “only Staff sees this page and they know what to expect” thing and not a critical problem.