I absolutely understand, it's just not hard to make scraper traffic appear as (or be) legitimate browser traffic and/or simply distributed across numerous IPs. Other technical controls all have trivial circumvention methods. There is legal precedent (at least in the US) suggesting that scraping public information may be permissible under law (see HiQ Labs v. LinkedIn). Scrapers only ever need to succeed once.

Under these circumstances, how can a website operator feel any sense of practical control over scrapers?