Exclude a class and all of its children - css

Question

I am loading global CSS styles but I need them to not affect one part of the page and all of its subcomponents. There are some old information but is there a solution now when :not() is a Level 4 selector?
Codepen example that is not working: https://codepen.io/LaCertosus/pen/PoaYeRj
I have a HTML structure that is not predefined, I do not know how many and what elements are around and inside the "red" element.
Visual example
<div class="parent">
<div class="_filler">
<div class="_filler">
<div class="block">
Should be red
</div>
</div>
</div>
<div>
<div class="child-lime">
<div class="block">
Should be lime
</div>
<div class="_filler">
<div class="block">
Should be lime
</div>
</div>
</div>
</div>
</div>
.parent:not(.child-lime) {
.block {
background: red;
}
}
/* Block is an example, in reality we don't know the class name */
.block {
height: 100px;
width: 100px;
background: lime;
border: 1px solid #000;
display: flex;
align-items: center;
justify-content: center;
padding: 1rem;
}
I have tried different combinations with :not() selector but with no luck. It works when I don't need to include all children.

Answer 1

add this into CSS file
.parent > ._filler .block {
background: red;
}
.child-lime .block {
background: lime;
}
remove this from CSS file
.parent:not(.child-lime) {
.block {
background: red;
}
}

Answer 2

Your question seems to be missing some details, but here's what gets you close (assuming you can't touch the underlying HTML)
.parent {
div:not(.child-lime .block) {
background: red;
}
.block {...}
}
There's an un-classed div element that turns red...but since your comments seem to require not touching the underlying HTML and using the :not pseudo, that's probably as close as you can get.