You sound like an outlier, I routinely interview senior engineers applying to Google and a massive majority do not pass the coding test. I would say half are not even in the ballpark of passing.
Well in SV all you have to do is work at a startup for more than a year to get "promoted" to senior/lead developer, so it's not surprising that many people applying for those roles aren't actually at that level.
By senior I mean 5+ years experience, not their job title.
5+ years is really the beginning of intermediate. 15 years is a better starting point.