That's what people said about Poitoed and Ninetails last gen as well. When one move or ability benefits the whole team then people will find a way to make it work. Besides, what is one relatively weak pokemon vs an entire team of bulky, strong AND fast pokemon now? It's like having an entire team with Swift Swim only with better coverage options and less shared weaknesses. Not to mention Shuckle, Galvantula and Leavenny are far from horrible. They're all pretty unique in some form.Actually there would very much be a answer, or at least a guesstimate of majority use. For teams you are up against, well most of the time it won't affect your own 6, just how you use them.
As for this move, people talk it up but it ain't going to see much use. The Pokemon that use it are far from acceptable to be in a OU final 6 team. There are far better Bug types to run (Volcarona in December and Scizor). The best case would be Galvantula, but then you would pass up much better electric types that are OU as of now. Jolteon, Magnezone, RontomW, and Thundurous T.
Also, stealth rock will IMO stay as dominant as it is. Hurting Pokemon on the switch is far more important then a speed decrease, made all the easier to stick with SR when the sticky web pokemon are very weak competitively.
This attack will find a niche. You may find the occasional Galvantula but this will hardly replace stealth rock. Teams running both? Now that would be cool to see that being adopted.
That said based on ubiquity alone and ease of use Stealth Rock will never be usurped. You'll always see more Stealth Rock than Sticky Web but there are surely teams that will run both. Shuckle alone can set up both and has Sturdy. It was meant for this role.