Did that contribute in her decision to end the show after seven years? Basically, in TV Guide around 1976, Mary Tyler Moore revealed her displeasure with the new "jiggle TV" (http://www.sitcomsonline.com/boards/showthread.php?t=290599) shows like Charlie's Angels. The MTM show really coincided with the feminist movement of the 1970s and MTM always wanted her show to be about the empowerment of women. So it's likely that popularity of Charlie's Angels made her feel that she had done a lot of work for nothing and it ultimately was a consideration in her decision to quit after the 1976-77 season (https://en.wikipedia.org/wiki/1976%E2%80%9377_United_States_network_television_schedule).

I find Mary's outfits sexy and revealing at times - so there's that

But she wasn't ONLY sexy and revealing. The Angels were more about that.

I’ve always heard that she wanted to go out on top as a ratings success like Dick Van Dyke did on his show so she ended it for that reason.

On the other hand I’ve heard MTM herself say in an interview well after the show ended that she really didn’t want it to end at that time and was very depressed afterwards. What ultimately ended the show was probably a complex series of events and decisions by several of the principal people involved.