We’re in full agreement here, all I was saying is that the menality that leads to user agent sniffing is likely the idea that engines that aren't Blink are so i

We’re in full agreement here, all I was saying is that the menality that leads to user agent sniffing is likely the idea that engines that aren't Blink are so incapable and will break the site/app so badly that it’s better to just rule out their usage altogether. Checking on a per-function basis (or alternatively, just not insisting on using bleeding edge features in the first place) is absolutely the way to go about avoiding brokeness.