Except that lead's toxicity has been known for thousands of years.
Seriously though, people tend to dismiss things they are know are bad if there is no immediate harm. Certainly they had no idea how incredibly pervasive the lead from gasoline would be, that it would be detectable at harmful levels in basically everyone. It is also hard to measure these harms. How much crime of the 70s and 80s could be attributable for example.
It was instantly obvious to anyone that using leaded gas esp. in agriculture would be deadly and toxic. The risk was ignored for profit, PR handled, underplayed. Even the chronic effects were known!
We even had an early alternative of just adding more ethanol to the pettol. But no...
It took 50 years of scientists trying to convince public how deadly this thing is, with varied success. And 30 more years for the bulk of the phaseout.
Who are “we”?
The same could be told about AI - content farms, generating spam that bypass spam filter, etc…
Some people knew them, majority of the public don’t
Then there was a big chunk of time taken out for WW2 where such considerations were pushed out. The issue returned later but then it was argued there was no alternative for years.
AI toxicity... We don't even know the risks. There's potentially no limit to the damage. We have some examples (metrics making echo chambers, automated classifiers giving people wolf ticket for no reason, amplified evil biases in conversational AI, fake news and deepfake generation) and some guesses for now. We do not even know how to begin to regulate it.
It's not even the same ballpark. Internet would be a closer comparison and it's still wild west.