The issue is that there's a single monopoly provider who very much likes forcing all of the client apps to support their proprietary API. When 70% of users are

The issue is that there's a single monopoly provider who very much likes forcing all of the client apps to support their proprietary API. When 70% of users are Gmail, and Gmail has a vested interest in not supporting JMAP even though it's better, it's a hard sell for other client apps to invest effort. The solution, of course, is monopoly regulation. AOL Instant Messenger was forced to interoperate and embrace standards. If our legislators had the actual courage to do their jobs in this day and age, Google would be legally required to shift Gmail features to using open standards like JMAP.