A lot of what the petrochemical industry does took over from other stuff or isn't vital, there just hasn't been enough push back against it.

Stuff like medicine, sure, crucial and very hard to find replacements for.

But single use plastics can probably be replaced 95% (the environment would appreciate it if we banned them), dyes are mostly not vital, synthetic fibers can be replaced 95% with minor critical impact, just using natural fibers, etc.

The petrochemical industry is just the cheapest option in many cases in a world driven by conspicuous consumption of non vital items.