I have quibbles with your quibbles.
"Like most people, I'd imagine, my ears and skills are a bigger problem than the weaknesses of whatever gear I'm using - if you don't know how to mix (guilty!) then the fidelity of your monitor speakers is the least of your worries."
Not that it doesn't matter, but that he's not able to take full advantage of the better stuff.
For the first quibble, I think this is the key part of his response:
"I don't want to be the guy who just tells everyone how great their lives would be if they quit their jobs, but for many people there's less justification than ever before for staying in a work situation that isn't rewarding for you. If you want to do stuff, go and do stuff. Who is stopping you?"
I don't read that as a categorical call for everyone to quit their job and endanger their family's security, and "if you want to do stuff, go and do stuff" can mean exactly what you say about continuing with your job while building up other work.