To provide historical context, 10 years ago there was a local dev infrastructure, but it was already so creaky as to be unreliable. Just getting the ruby dependencies updated was a problem.
The local dev was also already cheating: All the asynchronous work that was triggered via RabbitMQ/Kafka was getting hacked together, because trying to run everything that Infra/Queues did locally would have been very wasteful. So magic occurred in the calls to the message queue that instead triggered the crucial ruby code that would be hit in the end.
So if this was a problem back then, when the company had less than 1000 employees, I can't even imagine how hard would it be to get local dev working now