Antitrust laws are applicable when one company controls an entire market.
As has been noted exhaustively, Apple is a MINORITY player in the smartphone market. Antitrust doesn't enter into it.
MSFT, OTOH, absolutely WAS in a monopolistic position when the browser wars were raging, and was found to have abused that monopoly power. Apple isn't even CLOSE to that level of dominance, unless you define the market as "people who use Apple devices," which is transparently risible.