In terms of the best integration architecture, what seems to me the only long-term solution is something like the unified log architecture that Jay Kreps wrote about back in 2013. All incoming writes need to go into a centralized log, such as Kafka, and then from there the various databases can pull what they need, with each team making its own decisions about what it needs from that central log. However, SuperRentalCorp has retail outlets with POS (point of sale) systems which talk directly to specific databases, and the path of that write (straight from the POS to the database) is hardcoded in ways that will be difficult to change, so it will be a few years before the company can have a single write-point. For now, each database team needs to be accepting writes from multiple sources. But a unified log is the way to go in the long-term. And that represents a large change of process for every one of those 20 teams. Which helps explain why the company has spent 2 years and $25 million trying to build an API, and so far they have failed.
to;dr: decouple your shit, fools.