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