The formula for WRX and STI is outdated. They aren't legal for WRC anymore, and sedans in general are declining.
AWD is no longer an exclusive... many vehicles have it... and Subaru's CVT system isn't all that much better, and the manual gearbox options are getting rarer.
An economy sedan tarted up into a fire-breathing turbo AWD rally car thing is more than 15 years old now, and the people who grew up when that was the new thing, have moved on to larger family cars.
They have had their opportunity to make an STI version of Crosstrek and Forester, and haven't done it.
They had a flat-6 and discarded it.
They could have built an AWD alternative to the Mustang EcoBoost, but instead they produced a no-torque coupe alternative to Miata, without even the option of the drop-top lifestyle appeal, because Toyota wanted it.
They could have built a 718 Cayman/Boxster with Toyota as an MR2 successor. before Porsche even thought of putting a turbo-H4 in their car... but didn't do it.
They could have made the outback, or at least the Legacy Wagon into something that someone actually likes... like an affordable alternative to an Audi S or RS Avant... but no, it is also an old paradigm that is basically at this point a slightly frumpier CUV.
I used to be a BIG proponent of Subaru, and owned both and SVX LS-L, and a 2005 Legacy GT Limited 2.5 Turbo sedan with a 5-speed.
I haven't been a big fan of Subaru for about a decade since, when they showed repeatedly that they KNEW what people wanted, with their concepts... and taunted people by making their production cars into appliances instead.