The problem is Apple is corrupting SMS, which should be a public and interoperable standard. Google/Gmail is doing the same thing to email. There’s no technical reason you couldn’t have end-to-end encrypted text messages between iOS and Android.
I bet way more people would try Android if they could fully participate in group texts.
There are tons of apps that offer end-to-end encrypted messaging between iOS and Android (and Windows, MacOS, Linux fwiw). Apple offers APIs to allow you to associate your contacts with their ID in those apps so you can easily message them or share photos and files as part of iOS. The thing they are accused of is that they provide a great experience for users in their ecosystem on top of that.
I bet way more people would try Android if they could fully participate in group texts.