Pretty sure the "Arduino ecosystem" is more than just the boards. It's also a bunch of libraries that provide a standard interface to a bunch of different hardware as well as tooling to build, flash, and monitor those libraries. While I don't love those libraries or tools, they do a half-decent job of papering over the shockingly painful esp-idf (the equivalent libraries for ESP32 boards) which I understand to be one of the better embedded SDKs.