Even if he was acquitted, that doesn't mean he has shown his innocence. It just means they found a reasonable doubt about his guilt. It could still be more likely than not that he did it.
wtf. No, it means we don't have a reason to keep suspecting him.
Forget mere suspicion. You could have near certainty, and so long as there is a small but reasonable doubt, that is a finding of "not guilty" in criminal court.
If somebody isnt found guilty in criminal court it doesn't mean they are innocent and didn't do what they were accused of. It merely means that a reasonable doubt (or procedural error) was found to exist. Plenty of guilty people are found "not guilty" to a criminal court standard. Some then get sued in civil court (a balance of probability test) and are found liable.
If we still do, what's the point with the judicial system?
I think you mean what is the point of the very high standard of evidence in criminal court, and the answer is to err on the side of freeing the guilty rather than licking up the innocent.