Bear in mind, OP, that a lot of people on MN S&B are very concerned with trends, even though they insist they're not!
leggings cannot be frumpy or off trend, they're a multifunctional garment - perhaps those who wish to use expressive language about them feel that they don't suit them? And that's fair enough.
I don't live in a trendy city or repressed suburb of side-eyeing mums, lol, so wear leggings with abandon for hiking, long walks and other activities such as collecting moss, volunteering outdoors and mooching for stuff for sculptures.
I wear mine with a Patagonia insulated hoodie and big boots. Often with a rain coat over that. Not quite fashion week but very much current and appropriate for my lifestyle.
At home I may often wear soft leggings with a long chunky jumper on lazy days. I would not go to work or to a special event, dinner or city break wearing them.
Many of the current trouser/jeans styles are bordering on 'laugh out loud' to my mind; ludicrous stiff shapes with giant nappy-style rises to keep that tummy in....and the block shaped wide legs are hideous. Flapping about in winter in the rain, with a similarly blockish jacket isn't what I feel a 'good look'.
I am not a fan of jeans in general, but would rather wear a skirt if I had to (which I don't!), but then they're all ridiculously shaped too.
Fashion will convince ANYONE to buy ugly shit. You will notice how almost everyone on here suddenly (oh so naturally, lol) decided that the new blockish trew shapes suited them more, as soon as the trend shifted and other MNers gave them the nod of approval.
And to add, most people wear what is appropriate for what they're doing, which includes young people wearing leggings, etc, so they're not going anywhere no matter how many MNers can't get them up past their thighs.
People often associate cheap arse ruched legging with the, er, ahem 'lower class', which is certainly a thing, but out and about in the lands of milk and honey the more expensive ones are still going strong.