I've known a few physicians that have gone into ophthalmology after doing family medicine or another field. Very doable but at the same time, the competition for ophthalmology spots is much more fierce, especially when those said physicians applied for ophthalmology.
There are some downsides to ophthalmology as well, compared to more "cognitive" fields. Our reimbursement for procedures is constantly under the microscope for cuts, and not often there's pressure to run clinic like a mill, though I'm sure this isn't unique to ophthalmology.
There's still counseling regarding chronic conditions like diabetic retinopathy, glaucoma, etc. There are procedures and surgeries we can perform to stall and temporarily reverse things, but there's still an aspect of counseling not unlike your field. At least for me, compliance plays a huge part in whether my patient is going to do well long term or not - can't fix a retinal detachment/macular hole if the patient doesn't position, or doing a complex diabetic TRD repair doesn't do any good in the end if the patient's A1c is still > 15 for years and the patient refuses to take any responsibility.
Ophthalmology has always drawn exceptional candidates into the field that are contributing towards great things - I know I am biased, but some of the smartest physicians in general I know are ophthalmologists. I'm not exactly sure what you mean by ambition, but if you're thinking in terms of contributing to the field, while your drive would be welcome, you'll find out there are a ton of exceptional ophthalmologists doing great things for the field.
To me it really sounds like you're burned out. I would say perhaps maybe see if that is truly the case for you, and if so, perhaps addressing it may help reinvigorate your passion in endocrine. Even in our field, it's easy to get burned out in medicine.