I find their costumes cute but silly and I'm no 70's kid, but one of my favorite X-men stories The Dark Phoenix Saga was from that decade. I was introduced to it by the animated TV show from the 90's. I could have collected the action dolls with the 90's costume but completing the team was not an option made available by Hasbro. Up to this day, there hasn't been any 3.75-inch Storm doll in her white 90's uniform released by Hasbro. It has been around 8 years yet there is no sign that there will be one.
It must be annoying for other collectors to not be able to complete a team that belongs in the same period of time. No wonder people would rather cherry pick. They don't have the chance to collect them all. The only choice is to make the other characters yourself but would adults really have the time? There's alway better or more important things to do. Younger folks who have a lot of spare time can probably do it, but would they be interested in the older looks (90s below) of the characters?
I guess that is one reason this toy line is dying. They always leave an empty space in the roster of characters that they don't intend to fill.