Nobody would bat an eye today, but I think the concern back in '89, was the general perception of comic book characters being for a strictly child/family audience.
Batman was Adam West/Super Friends
Superman was the family friendly Reeve's series
Spider-Man was saturday morning cartoons and bland heroics.
BATMAN 1989 offered something very different. A bleak tone, a flawed hero... certain characters primarily motivated by sex, greed and power. A villian gets a bullet through the face, literally burns someone alive and falls to his death at the end. The violence was definitely more pronounced than anything seen (with these characters) before.
Comic book fans weren't shocked, but ''Joe Public'' was most certainly taken aback.
I’m actually going to do you one better.
89 wasn’t an out and out attempt at heighten realism to the point of Christopher Nolan. Where everything takes place in a plausible believable city and reality that we see every day.
It was an otherworldly Gotham, but everything within the movie and the city plays out arguably more realistically than anything we’ve seen since.
Like you said, Batman bleeds, Jack Napier gets a bullet through the face wound and it actually shows the gore. I would argue B89 has the most grotesque and realistic visuals of violence. The violence in TDK trilogy is brutal and was played out realistically, but we never saw its aftermath, we never saw broken bones or blood. The closest we came I think was when Batman drops Marone off a small ledge to the ground, and it’s implied he breaks his leg or fractures his knee.
I loved B89 for making Keaton an 80s action hero who wasn’t built like a musclebound freak like Arnold Schwarzenegger or Sylvester Stallone. He was the size and build like an ordinary man, just with extraordinary resources, motivations, psychology, and a costume that he literally has do you use for an intimidation factor for plausible and believable and functional effect.
Hell, through visuals alone we get an implication that while traveling the world Bruce Wayne was looking for vigilante suits of armor that would help his crusade not only to protect him but to intimidate criminals. King of the Whicker People, Because I bought it in Japan etc.
Until he settled or came up with the idea of the Batman.
It also gives a hint at his worldly training without directly needing to show it, or speak on it through dialogue.
He’s bleeding, at times due to fatigue or situationally gets his ass kicked, but he pushes through, survives, and lays the smack down. It almost shows him go through more adversity than any other Batman on screen we’ve seen since.
89’s Batman / Bruce Wayne is an absolutely huge bad ass.