My advice is to try all AIs (including Fulvestrant) and Tamoxifen before you give up. I did poorly on Exemestane and Letrozole and OK on Anastrozole. Please be aware that in a sense all cancer drugs are toxic. Below is something I posted on a different thread. But it might be helpful.

Alternative dosing letrozole: https://pmc.ncbi.nlm.nih.gov/articles/PMC4740217/
Alternative dosing tamoxifen: https://pmc.ncbi.nlm.nih.gov/articles/PMC11101371/
Alternative dosing exemestane: https://pubmed.ncbi.nlm.nih.gov/36951827/
Alternative dosing anastrozole: No studies that I could find.

According to my medical oncologist, the studies cited above show that lower doses of AIs or Tam lower estrogen just as well as higher doses. What these studies do **not** show is that lower doses are as effective as usual (higher) dose in reducing risk of recurrence. Of course, that doesn't mean that lower doses don't work--but there's no scientific evidence that they do.