Great post! I think there does need to be some very introspective reevaluation of commonly accepted technology hiring processes.
Obtaining negative signal solely from firing decisions disregards the many other sources of information that can indicate that an employee was not a good fit in a role. In addition, in a team, bad performance of a small number of members can often be masked provided the rest of the team is very good.
Personally, I feel we should reconsider the appropriateness of a 'cultural fit' interview. As a concrete example of how this restricts the pool of applicants: asking about remuneration is a red flag, which discriminates against applicants who are not from well-off backgrounds, because for them immediate economic outcomes are very important.