Even in countries where iPhones are ubiquitous the cross-platform nature of Whatsapp and the fact that everyone from your friend to your grandmother is on it, makes it dominant.
Yes you could use Slack to message your friends like you would on Whatsapp. The experience won’t be the same, and setup will be a hurdle. But would you use Whatsapp to replace Slack at work?
I think the term “compete” is used very broadly here.
do you have data to back up that claim?
https://www.similarweb.com/corp/blog/mobile-messaging-app-ma...
And as an alternative source:
https://www.messengerpeople.com/global-messenger-usage-stati...
"4. iMessage
Communication apps like WhatsApp are available on practically all devices, whereas native apps like Apple’s iMessage (and now Apple Business Chat) are limited to one provider.
However, the user base for iPhone is constantly growing in the USA. A lot of adolescents prefer iMessage to apps like Snapchat in order to reach out to their friends.
Since iMessage is a pre-installed service of Apple, there are no official messaging usage statistics as they keep those “in-house”. Looking at the ever-growing demand and distribution of iOS devices though, we can assume that the pool of iMessage users is growing. In the fiscal year of 2017, Apple reached a quantity of 216.76 million iPhones."
iMessage no worky for groups because you'd be excluding the Android users. Group SMS... I don't think anyone over here is even aware that's an option. I only know about it from Americans on HN saying they use it.