Plastic is the main concern when it comes to waste pollution. The main reason plastic products are so popular is that it's convenient and cheap. Hence plastic use is universal and widespread. To eliminate or at least significantly reduce the number of plastic products by replacing them with more environmentally friendly materials like metal, glass, etc. is infeasible at this point, instead, introducing materials that have the same properties/convenience but are biodegradable would be the best option.
The problem with biodegradable plastic is that it's more difficult to make compared to ordinary one and the production is more costly. There's an (in)famous comparison that the cost of resources required to wash a single item of metal cutlery is higher than the cost for making a single item of plastic cutlery, therefore it's cheaper to use plastic cutlery and discard it afterwards. That's how cheap ordinary plastic is. However, we have a strong motivating factor in place - pollution and it's getting stronger and stronger, so investing time, money, and efforts into developing good quality biodegradable plastics should be our top priority.
The companies producing plastic products could be incentivized to replace them with biodegradable plastic. The companies making biodegradable plastic should be highly financed by the governments to perfect their products and make them as environmentally friendly and at the same time as convenient customer-wise as possible.
The notion that biodegradable plastics are no better than ordinary ones because they don't fully biodegrade is misleading. It's true that most plastics labeled biodegradable today are not fully biodegradable, but biodegradable to an extent is still better than non-biodegradable at all. Thin polyethylene-like supermarket bags labeled "compostable" might be truly fully compostable, the level of compostability will depend on the type of the bag and the conditions that you'll compost them at. The products requiring thicker layers of plastic can be made from vegetable starch, those are usually around 70 percent biodegradable.
New technologies might soon make plastic fully biodegradable, recent scientific findings are promising in that regard, embedding enzymes that break down plastic into plastic products might be the key to creating a new generation of plastics with programmed biodegradation. Scientific discoveries can skyrocket when there's an urge and financial support from the government, covid vaccine development process is a good example of this.