Regardless of how history played out since then dedicated fans have paid homage to Jefferies and far surpassed FJ. Particularly over the past decade or so I've seen work I could never have envisioned back in the day. Fans are creating schematics and deck plans that replicate what we saw onscreen down to the set decor as actual ship fixtures.
Speaking for myself I'm still not quite wholly satisfied with my own work primarily because I lack first-hand access to original props, sets and/or original construction drawings. That said for decades I cringed seeing the TOS shuttlecraft drawn and illustrated poorly even by "official" sources. Eventually out of dedicated interest and frustration you take a crack at it yourself.
FJ's work initially fascinated and inspired us and then we went out and did it better several times over.