STIR/SHAKEN is a complex solution looking for a problem.
It MAY help a bit. The FCC used to very active in finding and fining tele-scum. I know I used to report things and get action. Then the sort of blew off consumer reports. Then the problem got big.
Like most government things, they created a committee to look at ways to stop the caller SPAM. Some very easy and quick things were put out, but they required the major Telecos to do work, they all got rejected and we got out of it STIR/SHAKEN.
Just cut off all inbound IP calls from a certain country, and the problem is solved. On, no, a lot of legit companies have call centers in the same cities as the scammers you say. Well, I say, too bad. They outsourced operations to get cheap labor, they also outsource their reputations. They can pull that back to some place that is not full of scammers or where they can be quickly reached by FCC the FCC and courts.