You are right: this is indeed no smoking gun (and it isn't hyped to be one). This is more like "we can't rule out life having created this, but there are alternate explanations which have also not been ruled out".

Unfortunately most of the evidence is going to be like this. The chances for better evidence would probably require a sample return of some sort, and even then I wouldn't expect a smoking gun (either way).

Well, not exactly. By my read, the known alternate explanations are very strained, only there for propriety. They don't have a really clear idea how this could have formed abiotically.