It doesn't matter if your ND child is lovely, or is a joy to be in your life. Wanting something different for them, and for you, is normal.
When every waking moment is about them, their struggles, your struggles, the fight for accessing services, countless appointments, assessments, judgements, juggling yours and other children's needs, work, life, money etc etc no one. None of this makes them any less lovable, likeable or wanted. It just means life is tough for you all on a daily basis.
Sure for some people its easier, they might have more money, more support, fewer issues, fewer disabilities just like for some people life is harder. But, for the most part, we are conditioned to say the right things. 'Yes thanks we are fine', 'oh no I can manage', 'don't worry, I don't mind'......
When we get pregnant we think of all the things our children will do. And they never include not be able to walk, talk, communicate, join in, have friends, live alone, go to university, go to the bathroom without a meltdown, panic because their red coat is in the wash and the million other things that people with a ND child face on a daily basis.
You are allowed to express sadness about what might have been, anger at the lack of resources, tears from sheer exhaustion. None of this means anything in terms of your child. It just means you are knackered and in need of a break. You are allowed to feel jealous about how bloody lucky others are that they can just get up in the morning and decide what to do, or that they can leave the house and be spontaneous.
You wouldn't be human if you didn't feel or think some of these things some of the time. You are amazing.