Is so far as you don't have to use the site, that's true, but they are legally enforceable, and you could absolutely be sued for breaking them if you upset eBay enough.
My understanding from hiQ v. LinkedIn is that it depends on whether you have access controls contingent on the terms' acceptance. If you have to make an account and agree to the terms to view content or place bids, it's illegal to violate what you agreed to. If you didn't explicitly agree to anything, you don't bind yourself by viewing the site, so breaking them isn't illegal. However, robots.txt qualifies as an access control and therefore is legally binding, so if an AI company is breaking that, they probably could be sued (see: eBay v. Bidder's Edge), but OpenAI follows robots.txt to my knowledge. Maybe the Internet Archive would be liable.
I haven't followed all the appeals though, and I'm not your lawyer.
