Not just Windows Mobile, but Blackberry OS, Palm OS, Symbian, not to mention the madlads hacking Linux onto feature phones (which eventually gave us PostMarketOS). iOS was actually very underwhelming when it came out, was(is) explicitly function over form and basically had(has) "it looks pretty and feels sleek" as its only selling points. Didn't even have third party apps whereas most of its contemporaries had them for ages by then.