[asadjb]

I agree with all three of your points concerning Mixpanel and what it would take to replace it with something similar. But I think you're being harsh when you say "This article epitomizes the old adage: software engineers are terrible at estimating".

I don't see anywhere that the article says they have replaced all of Mixpanel. It only says that they were able to replicate the functionality their client actually needed. I don't see them making claims that the solution they built is anywhere comparable to the full solution from Mixpanel. Only that it provides all the features their client needed.