Did not pay a lot of attention to politics back then, but seem to recall Reagan really stirring up a hornet's nest suggesting quarantining disease carrying poofters.
Reagan was like everyone else. He was making decisions based on the information available at the time. It's only after the fact that the CDC was able to piece together the at-risk groups. Remember, the original reports said only Haitians and homosexual men appeared to be at risk. We know now that HIV can have a really long dormant period where symptoms are nonexistent -- as in the case of the Canadian steward (aka Flight Attendant). Plenty of time for someone to infect countless partners.
There was also a reluctance by the CDC to work with the French. This new retrovirus was a chance to go down in medical and microbiology history. Lots of behind the scenes issues that kept people in charge, including Reagan, from understanding what the nation, and the world, was facing.
The first name for the disease was GRID: Gay-Related Immune Deficiency. It was also given the unofficial name of "The Gay Plague". The CDC had no testing for it. They eventually discovered that current tests for Hepatitis could find symptoms of HIV even though the test could not identify the virus itself. Since the virus suppresses immunity responses, they deduced that a test showing lower than normal white blood cells and other immunity related cells indicated suppressed immunity.
Anyway, people tried to politicize the disease the same way the Left is politicizing COVID-19 against Trump. Reagan could have put more money into R&D, but that could have actually slowed things down if the money was not spent properly. We still have no proven cure for HIV. While it's no longer considered a fatal disease in almost all cases as before, it's considered "chronic." If left untreated, survival rate is 6-9 months once diagnosed with AIDS -- the result of HIV. The prognosis with treatment varies case by case. Knowing that now, it's not rational to presume Reagan could have prevented the spread.
Even doctors were complacent until the disease showed up in the blood supply. I still can't fathom why people look to blame presidents WITH NO MEDICAL TRAINING AT ALL for problems caused by diseases. He relies on the CDC, Surgeon General and scientists to find the facts and answers. if they say, "Don't wear green," and Trump wears green, and the disease spreads, then I can see the argument. But when there is no data supporting the "no green" theory, it becomes a personal choice to either follow that advice or not.