You expect too much.
Bollocks.
What I expect:
Consistent clothing sizes: if I am a size 10 in one pair of trousers I don't expect another in size 8 to be hanging off me and yet another in a 12 to be too tight to do up. I cannot be a 6 and a 14 in the same store on the same day. I don't care how your sizing compares to other stores but an M&S 10 - or whatever size - should be consistent across all styles.
Clothes I might actually want to buy: I don't want frills, ruffles, sequins, ribbons, 'funky' embroidery, embellished denim (fuck, do M&S think we're all in B*witched?) and a sodding bow. I don't want them at all, but I certainly don't want them on the same item. Per Una: the brand for undiscerning drag queens of a certain age. And what is with the stupid flouncy sleeves? I want GOOD QUALITY BASICS IN GOOD COLOURS AND GOOD FABRICS. Uniqlo manage it, John Lewis manage it, Boden manage it, H&M manage it...why can't you?
Clothes that are designed for an actual human: last time I tried on bras in M&S, one appeared to be designed for those with one tit in each armpit, the other for those who have their norks stacked on on top of the other down their front. I may well be unrepresentative of the average tit owner but mine are roughly equally spaced on the front of me and cups in vaguely the same place would be handy. See also: not everything needs padding in it circa a 90s Wonderbra.
Clothes that look good on an actual human: if it only looks good on a 6ft size 6 model who has been carefully styled and lit, it's not going to do us ordinary mortals any favours. Stop courting the fashion press and chasing inclusion in the coveted 'Must Have Item' columns (after all, if everyone's got it you're going to rock up to a wedding and find four other people in it, aren't you?) and just produce some decent sodding tshirts and pants.
I would also draw your attention at this juncture to your tights. I laddered mine and had to buy some more so popped into M&S for replacements. You had two 'flesh' coloured pairs and I use inverted commas because I can't imagine anyone living actually has skin that colour. One could only be described as American Air Hostess Orange and the other as Recently Deceased Corpse. And they were such poor quality that they rolled down like Nora Batty's tights until the crotch was round my knees and I had to waddle most unbecomingly. Honestly, Tescos tights are a million times better.
To be able to find my size: time and time again I've seen something I quite like only to find that there's only one size 16, a couple of 18s and the rest of the rail is 20+. When I've asked staff for a 10 they say they've sold out. When I ask why they don't stock more of them, they say that's what they're sent by head office. Of course, stock all sizes but if you sell proportionately more 8-14s, STOCK MORE OF THEM.
Clothes that are decent quality: you know, stuff that holds its shape and isn't made of horrible man-made fabrics. Maybe even splash out and use a bit more fabric so that every top isn't too short - if I'm 5'2 and find your tops too short, how on earth do normal sized people cope?
And finally, decent stores: if I see something online I like I don't want to have to wander your shops like a lost sheep to find it. I don't want to have to try it on in grotty changing rooms. If I've bought it online I don't want to wait for half an hour in a queue to collect my order. And I certainly I don't want to find that the small sizes are right at the top of the racks (tip: people who are small probably aren't that tall) so I have to go and find someone taller to get it down for me.
It's not rocket science, it just takes a bit of thought. And it's precisely bugger all to do with the refund on a bath robe in 1992.