We keep encountering situations like this where a new chemical compound was introduced, becomes ubiquitous in our diets or environments and only later do we find out "Oops, it has serious health or environmental consequences."
It is worth the cost of slower introduction of new materials to take the time to ensure that those materials are safe. We're still paying the cost of introducing lead into our environment in a myriad of subtle ways. We still don't fully understand what the cost of the introduction of microplastics or PFAS is going to be. And regardless of the whether this particular study holds up under replication it is looking increasingly likely that aspartame is not something we should be consuming.
And what's most frustrating is that the people who profited most from these compounds never pay for the damage they cause to generations.
If a tiny increase in the amount of amino acids found in the body already can cause autism, that's really really surprising, to the point where it's much more likely that this result was just due to randomness.
If you take autistic children and test a hundred things that their parents were doing, one will probably come out statistically significantly higher, just by chance.