All time greats like Primo Carnera & Rocky Marciano showed signs of steroids but it is not affirmative.
Muhammad Ali didn't show signs of steroids. He didn't have superhuman strength [he had superhuman reflexes], he didn't walk through bigger men, he didn't go bald, he had longevity, etc.
Ali fought before steroids were common in sports.
His body never showed the signs of steroid use, he never bulked up or looked ripped.
His biggest asset was his speed, and the ability to take a good punch.
No one in this time era was ever accused of using steroids.
Steroids would have hindered a fighter like Ali, not helped him. His strengths were great boxing skills, speed, and reflexes. So in answer to your question he was an amazing boxer (with the heart of a lion).
Ali or as he will always been known to me "Cassius Clay" was without doubt the greatest fighter of his day if not all time. No one knows if he took Steroids I would like to think that he didn't and that he was just a great athlete.
Muhammad ali never used steriods because it never was reported. Anyone can be on steriods but we will have to blood test them to know the results. Some fighters go bald because of there genetics. Floyd mayweather and Zab judah went bald because it was in there genes. There fathers carried the traits. We should not accuse fighters because there is no evidence. A drug test will signal any doubts.
Muhammad alis trainer has reported that he took steroids and amphetamines...
His secret was fast reactions not muscular power.
That was just him. Great showman as well as fighter.