[hardwaresofton]

This. Was about to respond with a comment like this, but I think it's just better not to devolve into that argument (which has definitely been done before, countless times).

When Slack doesn't have some feature you need, what do you do? switch? pay some other company? develop it yourself? both positions have tradeoffs.

But by all means, if you don't have time to contribute to open source, then... don't, and buy the pre-packaged service -- I'm glad people think this way because it makes it easy for SaaS startups to profit -- which moves the industry forward anyway.