Even that requires a tailored suit, not an off the rack one. I just can't see the dichotomy the author mentions. Suits are clothes and they can be modern or not just like anything else. The differences are that older clothes were generally made to last longer, and that suits can be tailor made. But suits can be also cheap and low quality, they can be ill fitting, and here it doesn't matter if they're old or modern.

As for comfort, look at clothes you'd wear for relaxing on the couch or for extended periods like a long flight. A suit can be comfortable for a suit but otherwise they're mainly a matter of looks rather than comfort.