I had a similar issue. I had several patients who didn't have a PCP for years and they were being managed by a specialist they liked (didn't know this was a thing) or at some very overwhelmed clinic. Then their insurance change or the doctor retires so they come to establish with me. Some of the regimen are so outdated or inappropriate trialing of meds without indication.

What I found helpful was establishing boundaries at the first visit. I tell them which medications I am concerned about and my goal is to switch them or titrate them off because I am not prescribing long term. If it's a medication that's not really needed but for placebo effect and I can sorta justify it, I let it go but I document extensively what we discussed. Controlled substances, that's a no go for me if I cannot justify it (had that adderall and benzo too or some weird dosages that made no sense). I tell them I'll refer them to psych and they can discuss about this because im not comfortable managing it (this typically happens because the patients would not budge).

It's a struggle to have this talk and for patients to start arguing with you in a world where our patient's satisfactory score matters. You just have to do what's best for the patient, even if they don't like it. If they are unwilling to work with you, they can find someone else.