Wasn't Skype a proper mobile app decently early ?

The core issue was of course being a second class citizen on iOS, using a Skype phone number purely on mobile was real PITA for instance.

Personally I put a lot more blame on Google for everything they did on the messaging front.

I remember using a lot of very low quality, buggy Skype apps on mobile over the years. I don't think it ever approached desktop quality.

To be honest it didn't even work great on laptops that got turned on and off or went in and out of connectivity. The networking piece seemed designed for an always on desktop.