That's exactly right: the STi is not competitive. Subaru realised early this century that the Impreza was a van and began simply withdrawing, first their will then their money and their works team.
The 4dr Impreza remained viable in Group N for a bit but when the 5dr hatch finally was released Subaru were not in a homologation type of mood at all.
They still aren't.
I can't fault them. The new rules have made rallye boring. However none of that has fixed the chassis flaws in the Impreza -- not even dropping the Impreza name in favour of WRX or STi alone fixed that.
Subarus remain competitive in advertisements and -- from what I understand -- video games (though again, if and only if a CitroŽn doesn't show up, just like in real life.
They're tremendous road cars though! The STi has been improving in manners for years and the interiors are modern etc. For that I'm impressed.
Homologated motorsport? Meh.