Only things I use SMS for are purely utility: OTP, CC spend notice, bill payment, insurance premium, etc.
Only time I need SMS, i.e. when a family member or a friend travels to a remote area, internet, and hence, RCS don't work anyway. So, I had to switch to good old SMS. Since I deleted all RCS stuff, I use Signal/WApp/Telegram 99.99% of the times, and good old SMS for the rest of the situations.
There is a solution even without changing app: disable RCS. Everything real is fine with SMS, so ads are the only casualty. I wonder if this stupidity helps kill the already-struggling RCS.