I have no problem with Dr. Smith being female. Major West can also be female, male, black, asian, hispanic, white, etc. For that matter, Penny could be adopted, or it could be a mixed race couple. If Major West was female, I would still not mind a romance between her and Judy, provided it made sense in the story.
What I care about is the show is well written, the characters have good motives for what they do, and that the acting is well done. I am not a SJW, what I care about is the quality of the show. In the Dreamworks Voltron, Alura is darker skinned, Hunk looks to be of hispanic decent, and Pidge is a girl. However, the characters are fairly well written for a kids show, and the essence of the character has not changed for the worse. Pidge is still a giant brain, and Alura is more self assured. Hunk is the same old Hunk...comic relief. Both ladies are written as strong characters and are heroes, not weak damsels to be rescued, which is what you would expect of the pilots of the lions. So all in all, the changes to not detract from the story in any way, so to me it does not matter.
What I detest are changes that ruin a character. If Dr. Smith suddenly became a goody two-shoes character and became the hero of the series just because it was a female character, I would have an issue with that. If they used Dr. Smith to hit us over the head with SJW mantras like "resist" I would have an issue with it (sorry, Supergirl, but while your characters are interesting, your RL politicing is a huge turnoff) Dr. Smith is a self serving, incompetent, sniveling, backstabbing, two-faced liar that will betray someone for a crust of bread only to beg forgiveness when caught. Maybe it changes to be a little less obvious of a fiend, but Dr. Smith should still be the villain, no matter if male or female.