As someone said Landorus-T is the glue for the current OU-meta. Differently from the majority of the generations we had until now, none had such a big power creep as Gen 7 as a whole, mostly with physical attackers. Even though it's pretty bad for a meta to have 50% of the teams with it, as competitive is meant to make players work with their strategies, a really good option is always going to be more common in comparison to others. It's not like it's OP, it's just good in what it's made to do (mostly spam SR and Intimidate in the face of physical sweppers).
Would be better to not depend on it? Definitely. Is there anything that could be done to make up for its absense? Not even close. (i also wish I liked its design so at least i would have something prettier to look at)