Well the only way they could have done that was to fire Wheaton along with McFadden, and they didn't seem ready to do that. So Wesley stayed on board.
You're trying to put a moral choice on a production decision. Maybe you'd prefer that Beverly was in stasis in a bottom drawer in Sickbay somewhere during Season 2.
A lesser series might simply have recast the Dr. Crusher part. McFadden should count herself lucky that they decided to write the character out
, instead of simply replacing the actress and having The Child open with a scene where Wesley walks into sickbay and says "Hi Mom!" to a new
Or, they could have opened with Stunt Actor Beverly with some alien facehugger thing on her face, she's taken to sickbay where Non-Dialogue Doctor Extras work on her, and at the half-hour break they get the bandages off and she looks like... uh... Morgan Fairchild! Yeah! That's the ticket!