>>11218973and we don't know much about the effects of it. but many types of plastic contain toxic chemicals so there is always a certain health risk connected to it.
also many animals in nature suffer from ploblems connected to plastics.
our world is simply not adapted to this stuff being part of ecosystems. so having it all just laying around could stress these ecosystems and shift them out of balance. in extreme cases it destroys them(e.g. beaches that are litterally flooded with plastics. Or plancton eating microplastics and dying in large scale, tipping an ecosystem over) and thereby kills a lot of different species
at this point it is still difficult to quantify the damages caused by plastics, but it is certainly not affecting our world positively right now and IF serious problems arise then we can't really keep this stuff entirely out of our lives. It is already in our food, our beaches and oceans, and even some parts may be blown into your very own garden by the wind or someting.