It would be nice if we did, but while this would likely lower cancer slightly, I dont think it would come anywhere close to eliminating it. I think cancer is mostly a tradeoff for auto immune diseases and adaptation speed. A immune system good enough to prevent them, would also kill most all, and prevent any deviation from its template. This is particularly likely for the kinds of cancers which hit before 40.

In general, I think both the op, and this post vastly underestimates how little people actions affect the probability of cancer. Sure you can lower them slightly, but I have never seen anything indicating you can drop the odds of cancer more than 10% by clean living and pristine environments. Highly specific issues like very high radiation does concretely increase the odd's, but its barely noticeable outside of old school radiology nurses, or nuclear accidents. Things like a heavy tobacco habit does increase the odds substantially and significantly above baseline, but most people who smoke daily for a few years are still far more likely to die of something else. We can also infer that microplastics is less carcinogenous than tobacco due to its prevalence and negligible increase in cancer. Not saying its safe, just worth remembering that most cancer is better through of as bad luck, and very unlikely to be the persons fault. Basically cancer isnt anything you can expect that healthy habits, healthy food, or pristine environments could have fixed.

In the astonishingly rich biosphere there are exceptions to everything though, impossibly improbable things which had eons to occur. Concretely, we have yet to design a single antibiotic, geneditor or new trait, instead we find them. I care very little about the downsides for humans caused by pollution and global warming, but the loss of information which comes with damaging the biosphere is incomprehensible. In other words, I'm all for fixing both, but not at the expense of the biosphere. Fortunately, nuclear is a perfectly good alternative.