With third party fighters in Smash I think most can generally be sorted into three categories with acknowledgement that many have overlap between them:
-Notable Nintendo History - Mega Man, Simon/Richter, Banjo-Kazooie
-Significant to Video Games and/or Their Genre - Ryu/Ken, Hero, Pac-Man, Sonic, Snake, Cloud, Sephiroth, Terry, Steve
-Contemporary Popular Hits - Joker, Bayonetta, Steve (again).
Lara belongs to the second group, its just that her kind of significance doesn't register to a lot of people in the same way other potential fighters do; to the point where many would advocate a Doom Slayer or Scorpion because their respective relative prominence does take priority in their minds.