Wow is this ever wrong. Guaranteed issue is an enormous win for entrepreneurs. When you work for your own tiny company, you obtain insurance on the individual private market. Prior to the ACA and its guaranteed issue rule, insurers routinely denied coverage to family members based on cryptic "DO NOT COVER" condition lists. Coverage denial didn't merely mean the insurer wouldn't cover a particular worrisome condition (which is bad enough) --- it was a blanket denial of
any coverage at all.
Young male entrepreneurs didn't run into this problem because they were male, which conveniently dodges more than half of the "DO NOT COVER" list, and because they usually don't yet have families. But cross 30, get married, have a kid, time travel back to 2007 and try to insure your family. You'll see, like I did, how helpful the ACA is for startup founders.