So, back to the thrust of my question above: Why should anyone dwell on whether Lucretius interpreted Epicurus wrongly or indeed intentionally declined to include Epicurus’ atomism?
Perhaps because it is a body of writing that has transcended time, and that has given it a bit of a "special quality" that is different than just some "Joe-shmo". There is also the presentation of many ideas which are the basis for cognizing the material world, free from religion and superstition - and we still live in a world where a great many people are bound up by superstitions so this is still important for our time. Also, because much of what Epicurus wrote was lost but Lucretius has preserved his ideas.
Even if the science has now advanced on many things, what else is there that does what Lucretius does? Perhaps it is time for modern people to do what he did in a more up-to-date manner, while also still preserving the many subtle truths on things like the nature of the soul and death.