STIR/SHAKEN has barely started to be rolled out, and most major carriers don't fully support both protocols. Realistically the reason you've not seen a difference is that... well there's not been a change. The TRACED act stipulated that large carriers have to have it implemented by June 2021 (and several have... mostly) and that smaller carriers have a 2 year extension until 2023. The problem is that "smaller carriers" has a much looser definition than you think, which includes the phone systems used by most corporate businesses and most cheap/easy SIP providers (like NICE inContact, OnSIP, RingCentral, etc). That said, it'll be a couple years before you see the silver bullet you're looking for, and even then it'll be a couple more before all the kinks are worked out. (There's still some unanswered questions about attestation in smaller regional/local carriers. Also international partners aren't complying with the standard, so that increases the complexity.)

It's only really had any progress pretty recently. The "Traced Act" deadlines were only a few months ago, and I assume the carriers need some time to iterate on tuning it. Or maybe the FCC needs a few months of data before they can start smacking carriers around. I wouldn't give up yet.

I found installing NoMoRobo and paying the $5 a year has helped considerably.