Apple is very close to being a tier 1 company. Last time the promo committee for corporations met we gave serious consideration to promoting Apple but eventually decided more data points were needed of Apple performing at the next level.
In general the hiring bar is not as high and managers hire people they like not most knowledgeable ones. Also, because the culture is so toxic best talent and the ones that can leave the company, do so. I have seen a couple of very top engineers leave in the past couple of weeks due to favoritisms of managers and their questionable decisions. This is more common in ML and AI, since Apple has nothing to say compared to top tier companies.
After being on Blind for a while, It seems like tier 1 is probably: - consumer facing (I.e the layperson knows what the company does without it having to be explained) - makes a product people are emotionally invested in - can attract and retain top talent