The plastic doesn't need to last for thousands of years for our actual use, but the properties that make it last for thousands of years are also what make it desirable for our use: fully waterproof, impermeability to microbes, etc.
Yes, it is. Lasting for thousands of years is the same thing as (1) impermeability to microbes (mold / insects / etc...) plus (2) failure to react with local chemicals. Those two things are the things we want, and if you have them both, you last for thousands of years, because there's nothing to stop you from doing that.
Um, a stitch in time saves nine.
Are you just typing random words?
If a new material can take the place of some of those, that's a win. We don't need to replace plastic wholesale with a single new thing, there's no rule against using multiple targeted materials, we've just got used to material science being all about one material for recent history.
I mean, the simplest solution to this problem might be to leave that borderline uninhabitable hellhole and move to Europe where food in bamboo wraps or home-washed glass containers don't start stringing in matters of hours, but that's not an option for most.
Also, you might be thinking that some of those wrap materials were historically viable, but it has to be noted that the content inside were much less healthier than it is now. Medieval Japanese people were estimated to have taken as much as 50g/day/person of salt, which is literally 10x WHO recommendations, or like 1.5 cups per week, or one small backpack worth per year. Adding that much of salt to food is no different from marinading it in chemical preservatives, only much worse.
"We like it because it lasts thousands of years."
There are numerous other reasons for liking plastic ... in fact that's a very odd and unusual reason to like it. You say that the properties that we like about it are why it lasts thousands of years, but that's a very different statement. In fact, people have pointed out that we would prefer for it to have its likable properties but NOT last for thousands of years. So you've made a whole host of logic errors. You may not think so, but that's another consequence of the underlying problem here.
I won't respond further.