Plantinga’s argument defends the believer’s rationality; it gives nobody else a reason to believe. It’s defensive, not persuasive. Shouldn’t a site that promises evidence avoid leaning on it?

Correct, and it does not prove God and should not be sold as if it did. Its value is to clear away one bad objection (you’re irrational unless you can prove it) so that the evidential arguments elsewhere on this site can be assessed on their merits. Plantinga himself offered two dozen or so theistic arguments in addition to this defense. The other cases are where the positive argument is made; this one only removes a reason not to look.