I'd say not being able to message ~85% of smartphone users is a pretty big UX flaw.

You can message 100% of all smartphone users, it magically delivers as SMS. Also supports group chats with regular SMS users. Also supports MMS with them.

Given this pretty graceful degradation, what do you mean by not being able to message 85% of smartphone users?

Eh, that's terrible UX for everyone involved.

I'm more or less OK with the idea of Apple not developing for other platforms. However, they are actively hostile to anyone who has offered and tried to get interop working on other platforms, which is really a shame.

You really can call SMS a 'graceful degradation' while keeping a straight face? I call it intentionally crippling communication capabilities. Also, just say no to walled gardens.

I don't know about other countries, but in India at least, SMS's are generally paid and won't send if you don't have balance.

While WhatsApp/Telegram messages are actually free if you have got data.

And nowadays I get absolutely zero SMS's from people. All senders are now just bots and notification services.

How about non-smartphone, non-Mac users? Every other messaging app I can think of has a desktop client (even if it's a crappy one that requires linking to your phone, like WhatsApp).

That's not bad UX. That's a product limitation (a conscious one I might say).

This 'product limitation' makes user experience worse. Actually, it makes it unusable for most users.

Whether this limitation is intentional is irrelevant, the UX is still bad.

It’s also not the case that there is such a limitation.

https://support.apple.com/en-us/HT207006

A single contact / conversation can even mix and match.

Are you really suggesting that SMS fallback is a good enough way to message people in 2021? How about sending them a video? Location? Voice message? MMS? Does this crap ever work?? (In my country it doesn't work between operators and costs €.5 for one message)

(not the OP) two big UX gripes I have with iMessage:

1) For some reason, photos take forever to be received (and sometimes are not received at all) when I send them to certain people. Best I can tell is they're using older devices and/or are in poor reception.

This + I can't send a photo with a message attached means that I'll send the photo, then a message with context, but the person never receives the photo so it's confusing.

2) There is no clear way to dismiss messages from the list of conversations without deleting them. It makes it hard to find conversations later when I have to scroll through a bunch of stuff I don't care about, but may want to search later.

Notable gaps:

- Only available on iOS and MacOS

- Copy and paste is unreliable on both iOS and MacOS

- Plugins don't exist on MacOS

- Lots of fail scenarios for phone number switching.

- You cannot control encryption outside of the AppleID ecosystem (AIM supported user certificates)

- You cannot control identity for a corporate device, unless you use Azure AD.

That said, it's a great service that I use every day. But it could be better. Facetime is way worse and more disappointing from an Apple POV.

Isn't there a significant UX trap in moving an imessage enabled SIM over to an android phone?

The SIM isn’t iMessage enabled. The number is registered as a symbolic iMessage ID. That can be fixed.

Here’s how to handle that before you move:

https://support.google.com/android/answer/6156081?hl=en

Here’s how to deregister that later:

https://selfsolve.apple.com/deregister-imessage/

Basically just SMS 2FA showing you control the number to deregister.

As an Android user, the most obvious flaw of iMessage is incompatibility.