The issue is that if Google does create a competitor, or an open standards competitor is created, like RCS vs iMessage, Apple isn't going to implement that, or in any way interoperate with it. So even if Google or someone else made a better system that worked beautifully on Android and any hypothetical alternatives, but Apple only implemented their own system and refused to share, things would remain shit. Which is exactly where we are.

If Google had a popular competitor to iMessage, Apple users would feel left out, and that's what would force integration.

All they had to do was add sms to one of their chat apps, and people would have migrated over word of mouth for the extra features slowly overtime.