app.get('any_config_option') no longer works after upgrading from 2.3 to 3.3

We have an older codebase and we're trying to update to 3.3 for security vulnerabilities. We looked at the migration guide, but it doesn't mention anything about this issue. After we updated app.get('any_config.json_fails') and when getting any models from `const { Room } = app.models` they are undefined. I can't find any info regarding this.