Is your position that because we haven't yet prosecuted a President we should never? I think we shouldn't have pardoned Nixon and given Agnew more than a fine. Forgiving criminal behavior leads to more criminal behavior. If you want to extend that to Bill Clinton, feel free.
The reason Trump is different is that he was and is a danger to our country and blew up the peaceful transition of power, which he might well do again. The early unwillingness to prosecute and current acquiescence to ridiculous delays is only adding to the problem.