Isn't it more accurate to simply say that Delta developed in the world population? There was no vaccinated and unvaccinated population at the time, so it seems biased and somewhat spun to play the blame game by labeling it as developing in "an unvaccinated population", right? (I.e., if we're being fair and objective).
IMHO, with treatments like Ivermectin, we have to look beyond your experience alone. Even if it helps a HIGH percentage if administered early on, we could still end up with a false negative, specious conclusion if we restrict the observation only to the cases that end up in the hospital.
For example, if it helps 80% of the people who take it early on, and they get better, so you never see them in the hospital. Then, the other 20% that it doesn't help, get worse, and end up hospitalized or dead, and the faulty conclusion is drawn that it "does not seem to change their rate of decline once they reach the hospital", so it's summarily dismissed as not showing any benefit because the study or observation was flawed. IMHO, we've made too many mistakes like that during this entire pandemic from the start until the present. The agenda and extremely biased narrative has led to our best and brightest making too many basic mistakes and doing really bad science at times.