Loads of generalisations on this thread.
You can't shovel everyone into straights/skinnies and neither can you write off all bootcuts as Mumsy/frumpy.
Obviously there is way more chance of veering dangerously into the latter territory in bootcut jeans, but that's not to say all of them are.
And I'm sorry, but not every shape is going to benefit from a skinny or even a straight leg.
The thing is, if you find the Hoy Grail of jeans - a pair that is genuinely flattering - nips in the tum, reigns in the arse, slims the thigh and lengthens the leg, you'd be a mug to reject them because of someone else's perceived ideas of what is and isn't stylish based on a few bad examples of the genre, as it were. And that Holy Grail pair of jeans will be wildly different, style/cut-wise from one person to the next.
I have two pairs of said jeans and don't bother with any others. I wear other things on my lower half, instead of shoe-horning myself into jeans that don't do me absolute favours.
One pair is a pair of long-length Top Shop bootcuts, and the others are 7FAMK Kimmie straight-legs. Two very different labels and cuts, but both amazing jeans on me.
I am a size 10-12 and 5"9' (late 30s, in the interests of full disclosure), so admittedly am probably going to have an easier time that some other body shapes finding a really good, flattering pair of jeans, but I'm not going to bin a pair of bootcuts which do me all sorts of favours for no good reason.