You can block websites on an iPhone without Screen Time in three ways: Safari's own content restrictions, a DNS filter set on the device or router, and a filtering profile installed through Apple Configurator. Screen Time is simply the built-in convenience, not the only route.
1. Safari restrictions (free, no Screen Time). Settings → Safari → turn on "Block Pop-ups", and under Settings → General → Restrictions (older iOS) or Settings → Screen Time → Content & Privacy (if enabled) block adult sites. On current iOS, Apple pushes site blocking into Screen Time, so a DNS filter is usually the practical alternative.
2. DNS filtering (works in every app, not just Safari). Install NextDNS, CleanBrowsing or Cloudflare for Families, or set the DNS in Settings → Wi-Fi → your network → Configure DNS. This blocks domains across browsers and apps, including Chrome and in-app webviews, and it survives app reinstalls. Set it on the router and every device in the house is covered.
3. A filtering profile. Apple Configurator 2 (free, Mac only) can build a restrictions profile that whitelists domains and pins it with a passcode. This is the strongest option and the only one a child cannot remove without wiping the phone.
The limit of all three: they block domains, not searches or messages, and a VPN defeats DNS filtering unless you block VPN configuration too.
Where our app fits. Ultimate Phone Spy runs on Android 4.0+, Windows and macOS (features); on iPhone we have no product, so DNS filtering plus Configurator is the honest answer.