The main issue I see older people have with iPhones is unrelated to ui complexity. iOS’ worst parts are services/updates where the user is frequently asked for Apple ID passwords and shown confusing ads for Apple services like iCloud Photo Library that end up making photos more complicated to use as some pictures are now unavailable without internet. More parts of the iOS experience are getting unnecessarily tangled with server side services that require unpredictable prompts to get acceptance to terms and conditions, logins, and traps that make you set up two factor auth or buy an unnecessary subscription.