As much as I think Beeper's work on iMessage is important, apps like that do not and have never solved this problem. Because then you have different contact identifiers to contend with, the inability to make groups amongst those users, differing features, and the list goes on.
If you look closely at what I'm saying here, it's easy to compare it to what iMessage users say about why Android users create problems for them, and that's true. That's why messaging interoperability is important.
I cannot remember the last time I've received a non-spam SMS. The whole iMessage thing feels so alien to me. My girlfriend is an Apple fan-girl and has never used iMessage in her life. I kinda wanted to see what was special about it and when I asked her about it, she had no idea what I was talking about.
https://www.theverge.com/2021/4/27/22406303/imessage-android...
In short, Eddy Cue proposed in 2013 that Apple owning the best-in-class messaging app would be a win, and even mentioned the cost being low. Phil Schiller shut him down, arguing it would remove a barrier preventing iPhone parents from buying their kids Android phones.
That reads like anti-competitive motivation to me. In particular, it looks like tying, where two unrelated products are connected artificially. The wikipedia article on anticompetitive behaviors has a section on tying, and mentions another case involving Apple that bears some resemblance involving iPods being artificially restricted to only playing tracks either from iTunes or direct CD rips.
So I think the anti-competitive angle has some real merit.
The innovation claim, though, I have a harder time with. I don't see how releasing Messages for Android implies design-by-committee. They could just release it, like Beeper Mini just did, but without the reverse engineering part.