I think the biggest problem with Macnaghten's suspects- Kosminski and Druitt in particular- is they are founded in Victorian notions about the kind of person you'd have to be to commit that sort of crime- ie that you'd have to be visibly mentally unstable or your mind would have to 'give way' after the full blown mutilation of the victim in Millers Court.
130 years later we know that simply isn't the case and may actually be fairly unlikely- there have been plenty of serial killers including slasher types, who seem pretty much functional and are visibly sane- given the apparent medical knowledge, his ability to avoid detection and his success in talking prostitutes into dangerous situations even in the middle of the murder scare, I think it is far more likely he was Bundy/Sutcliffe/Milat style psychopath rather than the gibbering loon or suicidal doctor Scotland Yard seemed to be looking for.
With that in mind it wouldn't shock me if they were committed by someone who was never on the police's radar, and consequently will never be solved.
That said, as someone who was objectively a) a psychopath b) murderous and c) a doctor who d) lived in London at the time, George Chapman is probably the most plausible of the commonly raised suspects- at least he is someone we know legitimately did like killing women.
Forensic scientists say they have finally unmasked Jack the Ripper using DNA evidence; identifying Aaron Kosminski, a 23-year-old Polish barber, as the ripper. While the claim was originally made a few years ago, they have only recently published their findings for peer review. The peer response appears to be mixed.
From the limited material I've read since the announcement, peer objection appears to be founded on likely contamination of the shawl from which the DNA was extracted. In any case, the same suspect was purportedly identified as the ripper in the notations one of the detectives involved in the case; in which he he noted that Kosminski was positively identified by a witness who refused to testify.
Interestingly, both the silk shawl and the witness relate to the same victim; namely, Catherine Eddowes.