Why are "syllabics" in English lame? That is, why do I think them lame? Most of the time?

For a measure to be relevant, it has got to be perceptible in some sense. A Gestalt. It can't just be a number of something. Nobody I know of can hear Marianne Moore's syllabics. It's something that worked for her, in terms of producing the texts that she produced, but it isn't that relevant to the reception side of the equation. If it weren't in syllabics, it would still be what it is, which is prose divided up into lines of more or less equal lengths. It isn't meaningful in rhythmic terms at all.

Lame in the sense of limping along lamely. it's a yardstick, not a true measure.

Syllabics could work, of course. Very short lines would make the pattern more perceptible, but I'm not really convinced. It's like a course in the catalogue that's never really offered, but is theoretically part of the curriculum. Someone could find a use for its someday, but it's not that relevant. Don't even get me started on teaching children to write "cinquains."