Some of the merchants in Alibaba had been accepting crypto for years now.
Are you sure about that? I looked up Alibaba's payment methods and Bitcoin isn't listed as option, and as far as I know individual merchants don't have the ability to use other payment options.
There have been new crypto based marketplaces and these markets would surely put some pressure on Ebay to try something new.
I have seen none that actually pressure eBay in whatever form or shape. OpenBazaar looks like an eBay killer on paper, but its use hasn't been picking up, which has been like this for years now.
If something doesn't take off in its first few years of existence, chances are that it never might, especially with how there is zero marketing to attract new users. No marketing means no users, it's that simple.