If you're going to have monolithic platforms anyway (and you will, because designing for modularity is hard, whereas hacking together some random monolithic code is easier) they should at least be open source rather than proprietary.
Actually I disagree. Any time there's an Open Source tool that does everything for free, it's extremely hard to justify paying for a proprietary product that does it much better, because companies are cheap. There's many open source projects like this that are just terrible but a company will always use them first because they're free.
The answer isn't modularity, it's composeability, which is a significant difference. A modular program requires "integration" (tight coupling of APIs/ABIs) whereas a composeable program has loose interfaces which require virtually no "integration".
Drone.io is one example; you can implement any "plugin" purely by creating a container with an initial CMD entry that reads environment variables, and that program can interface back with Drone a number of ways (STDIN/STDOUT, REST API, database). Another is any application that just reads in or spits out simple line-by-line instructions or a JSON blob. Unix pipe based programs are the penultimate example. The dumber the interface, the easier it is to compose.
