And I agree that we shouldn't break things lightly, but in this case that wasn't possible. The options were let website scrolling be laggy and janky on mobile,

And I agree that we shouldn't break things lightly, but in this case that wasn't possible. The options were let website scrolling be laggy and janky on mobile, or break a very small amount of websites. (and your point is that things may never be updated, so no amount of "giving them the ability to opt-in to these improvements would ever help) And I stand by my thought that they made the right decision here, despite the very few easily upgraded sites that were impacted.