>All of these problems have been solved on the web

Have they? The solution to IP addresses is basically "use a VPN", which you could do also on a phone. SNI leaks have been around since forever, and despite eSNI, still isn't close to being widely fixed. There's MAC address randomization, but only because LANs and wifi networks are basically an unregulated free for all, so spoofing doesn't really matter. It's far less viable with controlled access networks like cellular. Some countries even have regulations banning spoofing/changing IMEIs.