We can and that is not something you can fix that is something you can only negate but it will be always there
Easiest way for you would be to have 2 tilemaps there
One where tiles are squares with outlines like you have here
And other tilemap beneath it where tile are full single color
And now you only change Z order of top one (with outlines) to go below one which have full colors after you zoomed out to some level
You could even do it via layers
Other thing is how you zoom out
For example you should not set zoom to 2,1 or 0,9
But anything that you can divide by 2
Like 0,8 0,6 0,4 and 1,2 1,4 … 4 4,2 4,4 and so go on
But again it will only negate effect and not get rid of it