Not at all. The reason Johnson should resign is that he broke his own rules created to prevent the spread of disease during a pandemic. Rules that he said MUST be followed, including attending funerals and visiting relatives in hospital or care homes.
He then, repeatedly, lied about his actions and changed his story. Not only in interviews but to parliament.
If the first reason, partying against the rules during a pandemic, is not reason enough to resign, lying to parliament (as well as via media) most certainly is.