Of course. I have seen this argument before. When we say "relatively straightforward" what is this relative to? SNI did not make possible what was previously

Of course. I have seen this argument before. When we say "relatively straightforward" what is this relative to? SNI did not make possible what was previously impossible. It made something that was always possible much easier and more reliable by creating a new method -- sniffing ClientHello. There is no such thing as "absolute" privacy on the internet, (IMO). There never was and there will never be. HOwever if our threat model is marketers/advertisers, the dichotomy, if we choose to view the issue that way, is "easier/more difficult" (on a mass scale) not "possible/impossible". Is it easier to passively sniff ClientHello from network traffic on a mass scale then to connect to 443 on a massive number of computers (or rely on someone else to do it)? Or is it more difficult? One method generates zero traffic and requires relatively less computing resources. The other method generates an inordinate amount of traffic, enough to trigger complaints from internet provider, and requires more significant resources. Today, we have both methods available. Before SNI, the additional, easier method did not exist. However, to be fair, I think there could be an argument regarding websites now using TLS with SNI because of the cost reduction of shared TLS hosting that previously were only only using TCP. Before they started using TLS, arguably hostnames could be sniffed from HTTP headers. Whether pulling hostnames from HTTP Host headers is easier on a mass scale than sniffing ClientHello packets, and whether anyone would do that for marketing/advertising purposes, is for the reader to decide.