There should be more research into the impact of micro plastic particles. That doesn't mean we should stop research into new applications. These things can, and should, happen in parallel.
Material science is providing a wide range of new and exciting options that go above and beyond what we could do only a few years ago. Dismissing something with essentially no understanding whatsoever is not helpful.
The problem with the plastics industry, the reason so many people are fed up with it, is the 'understanding' you speak of tends to lag their industrial application by many years. So we end up with a whole lot of "X is now known to have bad properties, but we already use too much of it to change now." For instance, virtually every thermoset plastic in use today is impossible to recycle, but there seems to be no going back. Their use continues to proliferate.
Some researcher building the next superplastic pauses to say "hey that's funny" and bam we've got a new formula that completely prevents the formation of microplastics.
Artificially constraining development is a great way to either miss an important direction of research that will unknowingly solve our problems OR just kill the industry leaving us with our existing plastics that degrade into microplastics.
Of course new developments should definitely run a microplastics study to make sure we don't make the situation worse. However "no more this until that" is a great way to freeze ourselves into our current less than ideal state for decades longer than we have to be here.
My understanding is that microplastics are a result of regular wear and tear, and I don't think a material exist that is immune to that. If anything, a new plastic formula may be created that hardens it enough to reduce the shedding to a negligible level.