I'm so sorry to hear your story and thank you for sharing it here. It illustrates how specialised eye doctors are and how important it is for people with diabetes to be seen by medica retina specialists. Diabetic eye screening programmes sometimes have problems persuading people who are attending the Eye Clinic for reasons other than diabetic reinopathy to go to screening as well. The person, quite reasonably, thinks that they are seeing an eye specialist at the hospital so if there are any problems with retinopathy they will be dealt with.Unfortunately, many of these eye specialists would not be checking for diabetic retinopathy so the patient is falsely reassured.
Please note, I am not saying this is what happened in your case, I just think it helps illustrate the problem. If you haven't already, it would be worth expressing your concerns about the first doctor to PALS. There would be an investigation and there might be some changes made to procedures which could reduce the chances of this happening to someone else.
By the way, medical retina specialists don't delay treatment unnecessarily - every treatment has risks so should only be given when it is necessary and not before. Some degrees of retinopathy will improve when the patient's glucose control and blood pressure improve so ophthalmologists sometimes give patients advice to try and improve control then monitor them more frequently so if the retinopathy doesn't improve but gets worse, treatment can be given as soon as it is needed. If the retinopathy improves, treatment (and therefore risk of side-effects) may be avoided.