Really really bad, for most people who contracted HIV.
AIDS is a condition or conditions that arise after HIV has worsened to a certain point — I believe this might be clinically diagnosed based on how many t-cells the individual has remaining; if that count was below a certain threshold, then the person could already be said to have AIDS.
Having said that, AIDS itself was essentially (or it presented) the same as it still is today. Except that the anti-retroviral therapies, which are now keeping many more people a lot healthier for a lot longer, were not yet known or available.
Therefore HIV was free at the time to run its full brutal course in almost anyone who got it.
As is now well known, although it doesn’t necessarily have to be an STD, it exploded in the US (and abroad) while basically mostly functioning as an STD. This was largely due to its very long incubation period and also its methods of transmission. Particularly in the homosexual communities (it flared on both coasts, in San Francisco and in NYC, first) men may have been carrying it — of course unknowingly — really nearly all throughout the often very sexually promiscuous 1970s.
A guy who had contracted HIV in, say, 1971 or 72, or 74, might not have really manifested serious ongoing symptoms until around 1980 or 81. In the meantime of course, he’d inadvertently passed it on (and possibly even been re-infected or ‘cross-infected’ himself) many times over.
Condom usage among homosexuals, including for full intercourse, was a rarity in those times.
AIDS manifested in people (and still does manifest) in ways such as rapid extreme weight loss (“wasting” syndrome), pronounced swelling of lymph glands, sores of the mouth or genitals or anus, ongoing fevers and heavy “night sweats”, ongoing fatigue and weakness, malfunctions in the person’s memory or thinking capacity in general (neurological disorders), neuropathic pain, etc.
The large reddish-purplish skin lesions of Kaposi’s Sarcoma (a rare type of skin cancer previously only seen in older predominantly Mediterranean men), or pneumocystis pneumonia (which was also pretty rare prior to the outbreak of AIDS), or CMV-related retinitis, and a whole horror house of other possible illnesses as well.
Such as cryptosporidium (which causes ongoing diarrhea); recurrent salmonella septicemia; candidiasis of the throat or lungs; multiple types of lymphomas; toxoplasmosis (something which usually won’t bother people with normal immune systems but in HIV/AIDS patients can become acute and lead to encephalitis); tuberculosis; Cryptococcosis - Wikipedia.
Many AIDS patients likely die(d) from pneumonias basically, though certainly not all.
The newer Anti-Retroviral Therapies have been allowing many or even most HIV patients to remain relatively healthy for a long time and to keep the disease from progressing to the point of AIDS. In many cases they can live a much longer life than they would have been able to in the 80s.
But, even with the ART, it’s still worth bearing in mind (particularly I think for younger people) that HIV nonetheless remains an uncured, currently incurable, very dangerous disease which is (or which can certainly lead to) a terminal illness.
And the treatment drugs themselves can have unpleasant short-term or immediate side effects for people (see also: Side Effects of HIV and AIDS Drugs), and some potentially heavy long-term effects on the body as well. See: Managing Long-Term Side of Effects of HIV Therapy
These drugs are likely quite costly as well (Cost Considerations and Antiretroviral Therapy | Adult and Adolescent ARV Guidelines | AIDSinfo) and treatment must be constantly maintained. Getting insurance coverage, etc (in the US for instance) can possibly be more expensive in some instances.
Not to mention all of the ‘social’ difficulties which are obviously going to arise as a result of being HIV-positive (whether undetectable or not; even if quite healthy in appearance and so on).
Regardless of how it is different (clearly it is much more hopeful and ‘better’ — relatively speaking) from the 1980’s, HIV is still a buzz saw of a disease which is nothing to be remotely played around with or taken lightly. It remains the same potential killer that it was when it first became known in the 80’s (it’s a pretty much surefire killer if you stop taking or if you can’t get access to the medications). And AIDS itself, if or when HIV becomes AIDS, remains every bit as bad.