Would you expect an 8 year old to do these things without help?

[OhImVisiblyOver25]

Brush teeth properly
Shower
Wash shoulder length hair
Tie shoe laces
Do and undo top button on a shirt
Sit properly on a chair at the dinner table

My dd is 9, has no other issues, and can do all. However, she only recently mastered laces and I try and supervise brushing teeth as she will try and get away with none! I think kids can vary a lot with some of these things

Bottom 3 yes
Top 3 no

To help motivate my DCs to get ready, they must be up, teeth brushed, been to the loo, dressed, and any items needs for the day packed/brought to me to pack before they can eat breakfast. They are very motivated by food! On days where they are exceptionally slow, I have been known to remind them that we will be leaving at 8.30 regardless of the volume of food consumed, and it makes no difference to me if their tummies are hungry and rumbly at school (obviously I do care, but I want to emphasise that they are causing any suffering to themselves and I am not prepared to be late because they faffed). Equally at bedtime, reading them a story is left until last. I remind them that every minute procrastinating is a minute less of their story.
Is there a part of your morning (or bedtime) routine your DD prizes that you can dangle carrot-like for once she's done everything else?

Would brush teeth yes but need reminded to do it for longer than 15 seconds!

I imagine quite a lot would need help with long hair to check it's done properly at that age. It's tiring rubbing and rinsing especially if very thick.

Shoelaces - hmm tricky one - some kids get co-ordination earlier than others, so I'd just keep encouraging the practising and help if necessary.

The others, by 8 and NT, yes.

Yeah because my DC all definitely did the above at 8, probably from 7 comfortably tbh.

I’m in my own in the mornings with her and the baby

Has she been an only child or youngest child up until the age of 7/8, and then a baby sibling?

If so she may be acting up for attention, or it may be that you were helping her with stuff more than you realised, and now you can't. Either way, the suggestion to have something she likes at the end of the process (eg breakfast and cartoons) seems a good one.

from experience of own kids and those of friends :

Brush teeth properly-not necessarily-should be able to give them a good go but still need supervision
Shower-yes as long as shower straightforward and not likely to scald

Wash shoulder length hair-might still need help

Tie shoe laces-possible but needs teaching and practise

Do and undo top button on a shirt-yes

Sit properly on a chair at the dinner table-yes but for variable lengths of time

My 7 year old can tie laces but only because he plays football and has big feet for his age. It took me a while to teach him. We used to race each other, one boot each.
He does a good job of brushing teeth but I still supervise.
He showers and can do his buttons.
Sitting still is very much a work in progress.

Brush teeth properly - yes and no. You should be supervising and brushing and flossing once a day until they are at 10.
Shower - yes
Wash shoulder length hair - DD needed help until about 10.5. Still needs help rinsing if she's tired!

Tie shoe laces - DD learnt this in the year she turned 9. Until then all shoes in her size were Velcro or button laces.

Do and undo top button on a shirt - I have no idea, DD has never had to do this. She could certainly button and unbutton a cardigan about 6 but that must be far easier than a small shirt button.

Sit properly on a chair at the dinner table That's entirely dependent on the food, mood and how much you engage them in conversation or activity you give them to at the table e.g. colouring. So at 8 yes, but not reliably or consistently or when you want them to.

My 8 yo DD yes. At 8 years old my DS struggled with laces.

All children are different and develop at different rates . However I think all children at 8 will need reminding about things. I think it's too much to expect them to just so everything on that list.
Doing up laces, top button an a shirt and washing their own hair are particularly difficult

Just because she can do it doesn't mean she doesn't find it hard. It's not lazy to not want to constantly do things you find difficult and making it a battle won't help. Lots of praise when she does do it but it's ok just to help out sometimes. Like a pp said she won't still be needing you to do it at 13

Mine can't do some of that but he's always struggled with motor skills so I don't shame him if he e.g struggles to sit properly on a chair as I think he finds that harder than other kids, for example his little sister.