I agree people should be mindful of waste, but it isn't always that easy.
Take celery - if I want to make a bolognese, I need about 3 sticks of celery. But I can only buy it as a whole root of about 12 sticks. I try to meal plan for things that will use the rest but it's not always feasible to do that for all ingredients, so I have leftover veg. I freeze it and make stock, but I only have a small freezer and I often end up making more stock than I use.
Same with salad - why does it only come in family sized bags? Why can't I get a half size bag?
We all need to make a conscious effort to reduce food waste but supermarkets have to do their part by actually providing food in small enough quantities to help people avoid waste without huge amounts of extra effort involved in batch cooking, freezing etc.
We've actually recently switched to Hello Fresh for 4 meals a week and it has massively reduced our food waste, but it's expensive and therefore not a solution for everyone (plus it has its own issues - excess packaging, travel miles for delivery etc).