Apple can release it because they are in charge of everything. You want to add VoWIFI or LTE or whatever, Apple will enable it in your carrier profile.
Android is very different, look at the Wifi Calling here where you can only use specified handsets with specific roms on specific providers. Also the hardware, you cannot just install a new version of the OS without it having the proper drivers/support for your device. So in those aspects you are very much dependant on the operators providing the updates, which usually means you get support for 6 months before their India outsourced dev team moves onto the next product.
That said, Android is getting better by putting a better HAL layer in place with various initiatives like Project Treble from last year.
TL;DR - Install something like LineageOS or some other ROM on your phone if you want updates.