[1] https://www.unep.org/plastic-pollution
[2] https://www.biologicaldiversity.org/campaigns/ocean_plastics...
[3] https://www.nationalgeographic.com/science/article/microplas...
[4] https://www.nationalgeographic.com/premium/article/microplas...
[5] https://scitechdaily.com/startling-discovery-scientists-find...
They tend not to be a good solution to anything.
There are a couple of ways of making degradable plastic. One is to add something to their manufacture so they break down into shorter chains which their supporters tell you will then further break down. These are generally referred to as OXO degradable.
Another is to use bio based plastics such as PLA or cellulose. These both have poor performance compares to oil based plastics.
All of these also require industrial composting where they add no nutrition to the compost, effectively just bulking it out. They [generally] do not break down when littered or even placed in a domestic compost heap.
There is also a problem because these plastics are virtually impossible to sort from recyclable plastics so if they get in each other waste stream the whole batch can be rendered contaminated and useless.
Finding it also odd that biodegradable plastics and safer alternatives are going quiet. As if the new scheme is to keep fossil fuel companies rolling, with the promise that one day a solution to get rid of incalculable mountains of plastic will be found. Don't worry, feel free to plastic pollute, because one day there will be a solution.