No amount of evidence ever means that a conviction is 100% certain - all that has to be proven is that it is beyond a reasonable doubt that you have committed an offence.  If three different and unconnected people independently attest that they have seen you break a car window then it isn't reasonable to believe they have all lied.

I still don't know what you want unless you are saying that if someone has been accused of assault, whether it was yesterday or 30 years ago that this shouldn't be investigated - what about murder, should that be ignored because it happened a long time ago?  It is at the interview stage that most accused are identified.  Granting suspects anonymity isn't going to work either - with social media, names are very quickly revealed and within their social circle and family it is almost impossible to hide from such an accusation.

So do you want such accusations to be ignored because of the harm the alleged perpetrator may suffer?  - If not then what do you suggest should happen if a number of individuals come forward with accusations about someone, whether the accused is a priest, a care home worker, swimming coach, 'celebrity' or anything else?