Isn't the Slack/Electron resource utilisation screenshot enough to prove an important point?

For most people: no.

They work around it. They buy new hardware and they're not sure why. There's massive business in selling people new computers (I'm including smartphones here).

For most in the tech industry: no.

Their job depends on them not understanding and/or not caring about this stuff. If they did care and acted on it, they risk losing a job to the next person who is happy to go "yes, sir", write more shit, and add it to the pile.