Out of curiosity, why exactly did you not mention THE virus that seems to behave most like covid: the Spanish Flu of 100 years ago? It essentially just vanished after milder variants and collective immunity were reached. No? Same for swine flu and H1N1. You seem to choose spwcific ones that remained “massive killers” (smallpox, HIV, etc). I totally agree that there is no “obvious natural path” towards milder variants. That part i agree on 100%. But why did you not mention the most “comparable virus” (to covid) and its phases? (Spanish Flu, hence Influenza).