I have a similar issue like this one. I'm using Cura 5.3.1, a Dremel 3D45 and PLA+ by eSun. The printings are almost perfect and repeatable. The only issue is about flat and large areas over supports.
Like the user of the linked question, I have no problem to remove the supports and they don't leave anything bad on the upper layer. Furthermore I enabled the bridge feature, and even more longer gaps (than the support density) print very nice.
Here a picture:
As you can see, the small trenches are clean, while the large box in the middle is awful. The supports have a density of 8 mm with the zig-zag pattern. As said before, even without support I can print very good gaps longer than 30 mm.
To have an idea of the dimensions, the hole has a diameter of 15 mm, and the larger rectangle is 60x45 mm.