It's more: unsure of cost-benefit for healthy males without comorbidities up to 40 and women up to 30 (especially those who were already recovered from Covid), the insanity of recommending the shots to pregnant women with zero data regarding impact on fetal development, reactivation of latent viruses like herpes simplex which might suggest some level of induced broader immune dysfunction, and the potential for vaccine enhanced disease or OAS (especially given the use of the long defunct Wuhan strain spike protein in ongoing booster campaigns).

Anyway, focusing on the specifics of the concerns is to avoid the more fundamental point, which is that doctors are not some cohort which one can implicitly trust to be guided by pure objective truth and scientific rigor at all times, nor are they a perfectly homogeneous group in lockstep agreement on all scientific questions.