Bob Blosl wasn't the only person to express the following wisdom, as I know very well others here, including Yellow House Farm and others have said it as well.
The "average" person, whatever the heck that is, cannot keep more than one true bred line going. At most two and even two is challenging. Those who try find they get all A.D.D. and soon are gone. Out of the hobby and gone from the scene.
Why? Because if you're gonna do justice to a breed, you've got to hatch, either yourself or combined with your partner(s) a hundred chicks per year, otherwise you fall backward. It's easier with partners to hit that number, but that number is based on a lot of experience and wisdom. With multiple breeds people either hatch only 30 chicks and soon those birds are going backward. Having 3 or 4 breeds, even at 40 chicks per breed, finds people overwhelmed with space, feed costs and all the attendant issues that come from large numbers of birds.
They're overwhelmed and they give it all up. Nothing ever much comes of their breeding programs.
This is why it is so often recommended that folks focus. The Attention Deficit Disorder thing will cause a lot of folks to be what Bob used to call "Here today, and gone tomorrow" He'd always ask the question, "Are you different?" "Will you be one of the chosen?" meaning will you be an exception and not fail?