I disagree. The language the app is written in speaks a lot about the culture of the software. If it was Java, I would expect something very different than if it was written in PHP.
If you think they're all the same, then maybe you need to get some more real world experience.
Slack is written in PHP, I guess people care more when they have to host it themselves. I wonder whether the stories of Slack's codebase being a hot mess are the real reason it's still not available to self-host.
If you think they're all the same, then maybe you need to get some more real world experience.