ESR often comes across as unbearably pompous and self-important, but here he strikes a very constructive posture of hard-earned humility and even tough love.
It may be that ESR was especially humble and constructive in that post. But honestly, I'd argue he was also objectively wrong.
Sure, you can get away with this when you're operating in "Founder only mode," and you're the sole contributor, but his point is valid. If you don't plan for the point in time when you have hundreds of developers working on several branches of forked code before you reach that point, by the time you do, your project is doomed.
Look, "Founder only mode" is when the practices of these large corporations with lots of people depending on them are the most valuable, because everything depends on you. There aren't other people who can fill in and do your job. You have to be able to do it all. You can't skimp on any of the areas just because you're just you. Not if you expect anyone to depend on you, including yourself 6 months later when you have no idea what the code you wrote there does anymore.
And you don't want to have to repeat yourself all over the place so you modularize. That's how it's done at the big shops too. It's good practice.
Considering how Linux is being developed today, I think Linus disagrees.