I agree with you. The legal system's job is to substitute for vigilantes. In this case the legal system doesn't provide certain services adequately, so the incentives favor vigilantism.

Also the presence of an executive part of the government which enforces law. If that is missing, the justice system is broken just the same. I don't understand why often we find it unfair when mob justice is administered (and it is unfair) but we don't find unfair that the police refuses to administer justice.

The police already foreclosed any access to your justice via budget priority. Now we're discussing various flavours of injustice.

Vigilantism isn't ideal, but what else is a person to do when law enforcement refuses to do its job? Not sure "just let it go" is a great answer to that.

In that case the US didn't have a justice system until 1963, as that's when people gained a right to a public defender: https://en.m.wikipedia.org/wiki/Gideon_v._Wainwright

Although since the states rarely fund it adequately, you often basically don't have one.

What, if you take the GP's comment as true, is very troublesome. But you didn't invalidate the GP in any way.