> Because progress will be driven by individual volunteers or corporate stewardship.
Works well in theory! In reality the incentives of open-source contributions are complicated and don't always pan out. This is especially true for complex applications, as they're generally harder to contribute to than small libraries/plugins...
The plethora of successful Apache projects is evidence that the model works for all sorts of software, from relatively simple (apache Guacamole) to complex (Kafka and ZooKeeper).
Apache is an example of an open source foundation being driven by individual volunteers or corporate stewardship, not proof one should expect such a thing to always pan out simply because it did for Apache. Much like the trillion dollar companies that give millions per year to the Apache Foundation what works for them doesn't necessarily apply for your typical case.