@mtinderscott2626 Teri (@windwalker) is no longer active on Mayo Connect. Since her post in 2017, Mayo has formed a Bronchiectasis and MAC treatment group, so if you are diagnosed you will be referred to one of them.
As for whether the "Big 3" is old school or not, research-based protocols for treatment of MAC/NTM have been developed. These include watch & wait with daily airway clearance, and several combinations of antibiotics, from two to five drugs at a time, depending on the condition of your lungs, the severity of infection, the specific bacteria (many types of NTM), the antibiotics to which it responds, and what a person can tolerate.

Here is a guide from 2019, but more options have been added since:
https://www.ntminfo.org/wp-content/uploads/2019/09/Guide-for-Patients-with-NTM-Infections-2019-09.pdf
This is somewhat heavy reading, but you can see it here:
https://ntminfo.org/wp-content/uploads/2020/07/NTMguidelines2020.pdf
Here are the 2025 European guidelines, which will likely be adapted and published in the US:
https://publications.ersnet.org/content/erj:::66:::6:::2501126.full.pdf