I don't know how Slack operates as a business, but if they work like most companies I've worked for, every employee gets a similarly spec-ed out machine. Maybe it's a MacBook, maybe not.

But at least some people should get machines that are a few years old - because that's what the users will have.

This used to be a classic problem in PC game development - developers get kitted out machines (because they need to run more heavy duty tasks during development, or run GPU debug code, or need to test the limits of the engine, or maybe just because they are gamers themselves so they buy newer hardware more often), so they tend to miss the mark on how powerful the average consumer machine is and only optimize code until it runs smoothly on their machine.

Shush, be calm. Just keep writing more javascript...