How do you ask for change without being too critical?

i don't know if i agree that dismissives are "overly critical".

I'm not sure what kind of issue you are mulling over, but i myself think it's normal and within bounds to have preferences and state them.
there doesn't have to be anything critical about it.
in the clothing example you gave (which isn't an area i would be likely to have a preference,unless it involved indecency or offensive odors) , i think it's fine to have a preference and state it. there doesn't have to be any value judgement involved.

So, say you don't care for the article of clothing.

"Babe, you know i love ya. I have to confess, when i see you wear the yellow and black zig zag sweater, i think of Charlie Brown. It's not that you're not pretty. it's that the sweater reminds me of a little bald dude. "

I'm being humorous. But surely there is a way to voice a preference without being critical.

Every adult knows there are articles of clothing which are flattering to some, unflattering on others.
It's not trying to change someone to say so.

Trying to change someone would entail some kind of repercussion to them not agreeing to your request.

that's the thing. Say you'd like your wife to pitch the yellow and black zigzag sweater. But she loves it! Then at that point, her freedom to wear whatever the heck she wants prevails and you get to be a decent guy and suck it up. Accept it, and choose your battles.

It comes down to boundaries, but also the freedom to have an opinion or a preference. And the ability to remember who you're talking to, and the care and respect they are worthy of.

Bad:
"That sweater makes you look like a fat bald dude named Charlie."
"You look ugly in that sweater"
"what a stupid sweater."

There are many sweet and even humorous ways to express an opinion or a preference without being critical or demanding.

It depends, really, on what kind of change you're looking for, though.

i myself tend to very much be a "live and let live"
person. i don't mind what others are doing much as long as i have lots of space around me, and my own personal space to do exactly as i please.
i am particular about my preferences for myself.
there's a reason for most of what i do, and i value my autonomy and my pfreedoms a lot.
this is why i prefer to live alone and enjoy my own little habitat.

being "picky" can be a defense, a habitual wall against ones own availability, and vulnerability.
it could also be a kind of perfectionism projected outward , but reflecting hyper critical attitudes toward the self, i think.

it may be as simple as catching oneself in the act of rejecting something about a person, and giving it grace or looking at it as a personal freedom to be exactly as is, without interference, the way we do enjoy personal freedom as independent creatures.

There is the concept of personal freedom that feels like a gift when you give it to people.
letting go of any expectation and allowing that person to be completely as is, and make a small sacrifice to accommodate it, can relieve discomfort quickly.

letting go of that internal resistance to what is -!: embracing it, can sometimes make a quirk endearing, when you realize that is the unique fingerprint of the individual.

It's that generosity, that grace.

i employed that with my previous partner and it made me happy, and it made him happy as well.

agree on all points, ocarina.
and, without compatibility in core values, i won't be in close enough proximity to ask for any needs being met.

To me, the progression is something like this:

boundaries help me choose a suitable relationship,
one with values aligned. no need to constantly assert and defend boundaries. the foundation is there.

with values aligned, a good deal of grace and generosity goes toward acceptance of quirks.

my own need for personal space doesn't hamper emotional availability- i can balance these well and enjoy it.

the right partner for me will allow me my freedom as well, will be able to reciprocate the freedom i extend.

i believe in this way of being, for me.
it's aligned with who i authentically am.

for me ,as avoidant, i don't identify with the issue perhaps because i don't cohabit, and don't intend to.
in my opinion, the issue of focusing on petty shortcomings is not at all an avoidant one, it spans all attachment types that cohabit.

i don't look to the literature as an authority, either, unless it's something i can identify in myself and other actual dismissives i know.

The reason is that so many experts on so many topics publish so much literature and even studies that draw conclusions that are disproven by yet more experts and studies over time, as more is learned and understood.

the understanding evolves, and many things are revised over time.
i think a lot of the literature on Dismissives is lacking!
and, geared toward the male gender.
obviously, females have some differing tendencies innately, as well.

Desire and intimacy are two completely different things. Both are helpful in a love relationship, but the things that create desire include distance, polarity and mystery. Those actually decrease comfort and intimacy.

It is rare to have both. Especially in the long run.

Unless you have the exact same habits or outsource a ton of cleaning work, it is inevitable to have some irritations in married life.
There is deep stuff like values, and core beliefs that must simply be compatible.
Then, there are habits that can not easily be changed: How often one changes the sheets, smoking, diet, social life. 
Then, there are easily adjusted and also easily acceptable things like the ugly sweater.

Mostly I expect this to be about the second category. What I see is that most cohabiting couples have at least one issue here. Some adjustments take place, some compromise but it never ends in full satisfaction.
My aunt smokes and my uncle hates it. she can´t quit but smokes in the shed.
My friend is a neatnik and her live in boyfriend is happy in a mess. He fully adjusted his hygiene, but when it comes to keeping a house tidy, he takes many a shortcut.
My other friend complains about her boyfriend loving junk food. He will eat well when she cooks it but on his turn to cook there is more often pizza, burgers.

I think striving for decent compatibility in this category is really helpful, but I would also expect to deal with some differences.

When we see someone twice a week, we may not always be on our best behaviour but we can be more different while still in harmony, plus desire stays stronger with less effort. None of the housework issues really matter; if we go over to a man´s house for dinner, it hardly matters if he does the dishes right away or in 3 days as we will be in our own house. Nor does it matter if he has friends over almost every day because we have peace and quiet at home. Or if we get drunk every weekend, he will not see us hung over. Nor will he care if our bedroom floor has a rug of dirty panties.

The choice to cohabit or live apart is a beautiful one to have, each has benefits.