Why don't you like Mageplanar speakers?

...But, I do like Magnepan speakers, but, I like a few (and I do mean a few) other speakers more.

For a basic box speaker to be really inefficient is something of a design flaw. However, if it's not a box speaker, then I think different standards apply. It's also just as easy to say that low wattage amps are a design flaw since they don't match well with really good sounding low efficiency loudspeakers.

Maggies were born in another era when SETs were the not buzz. It was an era of very large ARC tube amps that only made 110-150 wpc but were biamp'd into tympanis with unprecedented results. They are a small company that has changed little, offering its time tested formula at ever more reasonable pricing compared to an often ludicrously priced competition. It works for Magnepan, if it does not work for you, they and you can live with it.

It's also worth noting that there are planar magnetics that do use neodynium ribbons and give you amazingly high efficiencies, like the Wisdoms and Graz's Apogees. However, one look at the price of these and most people will gasp and go back to the Maggies and a more powerful amp.

Magnepan does use neodynium magnets in some models, where nothing else will do the job.

"I do not like thee, Dr. Fell
Why this is I cannot tell
But this I know and know full well
I do not like thee Dr. Fell"

Your taste is your taste and asking for explanations will not change it.