Well, WHO has in mind some steps that Reagan could have taken that would have limited the spread of the epidemic, but it isn't the sort of thing the Hollywood types or the AIDS activists really want to consider. Legal mandatory quarantine, for example (they'd be screaming "concentration camps" in ten minutes), mandatory testing for identified risk groups (imagine the reaction to that one!), investigation and publication of sexual histories of victims and their known contacts, forced closure of known vectors such as bathhouses; even in the United States public health has powers that not many are aware of, and many of these - mandatory quarantine, for example - have been reviewed by the Supreme Court and passed. (Some simply astounding steps were taken during the Yellow Fever epidemic of the early 19th century including stationing troops around infected towns to ensure that no one got out to spread the disease).
So, yes, there were things Reagan could have done that he did not. If he had, the ones doing the loud complaining now about inaction would have been the first and the loudest to scream about them.
CUBA is a world leader in aids treatment. This commie paradise does have mandatory quarintene of all HIV positive people on their island.
They also do not mention that 92% of all new aids cases in the USA are in homosexual men.
The one person that could have done something to stop the AIDS epidemic was the mayor of San Francisco who could have ordered the closing of the bath houses. Of course, that would have spoiled all the "fun", wouldn't it?