TOTALLY UNNECCESSARY - OFTEN CRAP FROM CHINA (or some other place that manufactures easily breakable and discardable crap) - YEARS - SOMETIMES HUNDREDS - TO "BIODEGRADE" - the WORLD does not need the pollution!
ARTIFICIAL CHRISTMAS TREES. A Germanic Pagan custom that spread throughout Europe and brought to the U.S. and other parts of the world - supporting electric lights, various decorations - sure a tree can look beautiful, even inspiring. Those little lights are so fragile that they easily malfunction and break so you have to buy more.
If you must, buy a live tree that can be replanted, use your old decorations or make new ones from biodegradable materials - or go without. If it's Christmas in your heart, it will still be Christmas.
So much razzle dazzle decorating is crap that breaks and needs replaced. You do not have to recreate Whoville to have a beautiful holiday.
This will cut down on the Christmas tree bonfires too.
Consider putting your ornament collection in bowls to set on tables...
ARTIFICIAL PLANTS and FLOWERS. Ever think it's a real succulent and it's plastic? Some people use fake plants outdoors as well as indoors. If you are too busy or lazy to water or don't have a green thumb go without.
For gifting stop the bouquets that will be dead in a week and go for live plants that can be transplanted or kept in the house. If you must have cut flowers, consider using them in a compost heap. For weddings and other events consider live plants with just a few cut flowers woven in.
PLASTICS: Plastic has it's place but everywhere should not be that place. Oh the plastic shit all over the sidewalks waiting for landfill pick ups. Especially children's broken toys,
It's out of your site but not really gone away.
FAKE GRASS which is really plastic or synthetic carpet. Really bad for the environment. Weeds will still poke through at the perimeter. Whatever you use as a grass substitute, you still need the natural drainage that actually filters into our aquafirs. Consider having your own little subterranean clay "pot" beneath your soil that will retain rain water. Plant over it and you'll reduce how much water you need to grow native plants and small bushes or trees.
BOTTLED WATER. More plastic - and it will leach into the water if you reuse the bottle. Three reuses is all that's suggested for most of these plastics. Some of us remember life when we did not take water everywhere with us. Maybe the earth was cooler then, but we were alive and well without guzzling huge amounts of water. Water can be filtered at home and taken with you in aluminum or other containers.
This is the short list.