I think your analysis failed to identify the root causes. Based on my observation having worked within the court system, the biggest problem is that courts have too low a standard for the submission of "expert" evidence. That precludes courts from distinguishing between real science and fake science (e.g. most forensic "science").

Courts understand that they can never be subject matter experts, and give great deference to people who call themselves experts (doctors, etc.) The real failure is the mainstream scientific community's failure to police fields that hold themselves out as being "scientific."[1] The National Academy of Sciences did a paper several years ago, where they took a look at the state of forensic "science" and collectively gasped: https://www.ncjrs.gov/pdffiles1/nij/grants/228091.pdf. But then they kind of just let that go.

If scientists were as politically-involved about forensic science as they are about climate change, we'd see major changes in the system.

[1] Engineers and doctors, in contrast, have done an excellent job policing their fields through their professional organizations.

Isn't someone's "expert" status up to challenge by the opposing party though?

Yes, but as a practical matter, the accused have little credibility when challenging an entire field of forensics. Both because the obvious self-interest and because of the lack of any scientific credentials on the part of the lawyer challenging the expert.

You can't get another expert to come in and say "bite mark analysis is unreliable." But given the wide variety of individual views among experts, a single opinion by one expert condemning an entire field doesn't carry much weight. In these situations courts look for scientific consensus. The problem is, the scientific community hasn't deigned to establish a concensus as to forensics. Not because they wouldn't mostly agree that it's pseudo-science, but because they don't consider it their responsibility.

It looks like kind of an uphill battle when discrediting your opponent is based on discrediting their field rather than just them as an individual (and it's a field that courts have become used to relying on for evidence).

All kinds of evidence analysis belong outside of police agencies and prosecutors' offices. Evidence analysis should be independent and not beholden to the criminal justice system. It should serve the cause of exculpation is that is where analysis leads. Perhaps it should be a branch of a state science office that also serves environmental protection enforcement and other functions.

Otherwise it will inevitably lead to the use of junk science and to systemic and individual corruption.

In the case of IP addresses, such an arrangement should be structured to advise that a warrant should not be issued unless multiple sources of hard evidence point to a particular location.

It does, however, allow those wealthy enough to hire a stream of expert witness to cast doubt on the technique in front of a jury and thereby win at trial while still convicting those who can't afford that.

The naive part of me still hopes this is just an unintended side effect.