eBay could do something about postage times and rates if they wanted to and should.
Simply they would make it policy that if you have an ebay store or a volume of business X big, perhaps a tiered system, then your services need to be commensurate e.g. accept returns of product, standard warranty periods, postal times etc.
‘a slow boat from China’ I believe is the real reason, waiting for a shipping container to be filled and surfaced shipped including intermediate ports en-route.
One of my pet annoyances re eBay is a product having a less expensive price, often much less than the cost of the item, and making up for this with overly inflated shipping rates sometime of hundreds of dollars. This should be stamped out. Delivery costs should match the actual freight charges. This way you can actually compare product features v price i.e. bang for buck, across several suppliers.
As we get more seasoned with difference selling platforms we learn the idiosyncrasies and how to spot the more reputable businesses. Good luck trying to get Google on the phone BTW. Cheers.
