I think the solution here would be to write a hand-written letter. Sure, someone can make AI write a letter with some kind of contraption holding a pen (I think StuffMadeHere did something adjacent to this). But it would likely be more obvious, plus it requires physical actions and a stamp. All things that low-effort AI spammers aren’t going to bother with.
Heck - I have seen some in the mail from the "sell your house for cash" companies - typically behind the friendly, "homespun" personable facade, it is a REIT (real-estate investment trust) - or something similar...
(Myself, I can tell that these are mass-generated - but I am (at least also at this point in life - who knows when I get much older) easily able to tell a scam email, phone call or txt-type message - I can typically spot the signs - but those signs are typically there to "weed-out" the people that won't fall for the scam anyways...) - but my non-cynical, non-technical, non-paranoid friends and family need assistance spotting these...)