It’s not pedantry to point out your word choice was so completely wrong. Illusive is descriptive of things that are illusions (a mirage is illusive water); elusive is descriptive of something that is hard to find
“Correcting” someone in a casual setting when they clearly communicated their ideas in a way that was understood by the majority of the audience without issue is pedantry, or more specifically linguistic prescriptivism. If their meaning was unclear you’d ask what they meant to say, when you tell someone what they meant to say you obviously understood them and are just being pedantic.