This is a subject and category where there are millions of misinformed individuals. When foreign plants and aliens are discussed you will know what they mean when you read this post. When there is a reference to an alien plant or an exotic it certainly does not mean it is exotic due to its gorgeous looks but that it is not an area native.
Make no mistake it is not the same as an invasive or noxious plant as these terms refer to something different all together. Where noxious is negative term, these terms are neither negative nor positive. It simply means you are talking about a foreign plant.
That being said do you also get invasive immigrant plants such as the kudzu vine that smothers any other plant it comes into contact with and take over completely. Then you get exotics such as most roses and peony and they are gorgeous and hundred percent non-threatening to other plants or the environment.
It is rather silly to ban all exotics as it might as well being banning foreign food from menus too. It is much better for people to understand what an invasive plant is in order for them to truly enjoy planting exotics too. To use an example of a gorgeous invasive plant like the goldenrod you will find that if you plant goldenrods in a meadow or your garden among your lush flowers soon you will have nothing left but only goldenrods.
If you are a gardener you will know some plants grow exceptionally well were as other which you want to grow, often fail. These plants that simply take over like all the kudzu species even jump garden fences and walls and make their home wherever they can. The downside is that most are not aliens and exotics with many invasive plants being natives, yet pests.