I am saying this as someone who has had repeated and ongoing issues with WP Engine as a hosting platform: no, Matt Mullenweg was not even valid in his basic assumptions motivating his lawsuit against WP Engine. The idea that a hosting platform is leeching off the WordPress ecosystem is absurd, for two reasons:

1. WordPress is free and open source software, developed under reciprocal licensing (GPL). Hosting companies are neither legally nor morally obligated to contribute back to WordPress core. They are already a beneficial part of the ecosystem.

2. WP Engine was contributing back to the WordPress ecosystem, just not Matt Mullenweg's corner of it.

WordPress is a modular platform and plugin and theme developers are just as important to WordPress's continued success as core development is. WP Engine happens to own Advanced Custom Fields (ACF), which is basically WordPress's answer to the Drupal Fields API[0]. ACF is what lets you add arbitrary fields to WordPress's page edit screen without having to write a bunch of custom metabox hooks and forms. It was a huge timesaver before things moved to page builders[1] and it's still useful even if you're using a page builder.

[0] Formerly Content Construction Kit

[1] Full disclosure: I hate Gutenberg. It is not WordPress, it's a React development kit tumor shoved inside WordPress. Any other page builder would be preferable.