Hi, I am new to the group. I know this is 5 years old, but I wanted to give you my advice.
I encourage your plant-based, flexitarian type diet. The Mediterranean diet has shown some benefits with T2, especially because it centers on a variety of whole foods, fruits, veggies, nuts, seeds, legumes, and good fats. It has limited amounts of processed foods, which is quick to be digested and then spikes blood sugar.
In general, a low glycemic index diet is good to strive for. Have you considered supplements to use as well? Like chromium, bitter melon, vitamin c, cinnamon, or Biotin? These can help level blood sugar.
Also, I am sure you know, but exercise is a great tool as well:)
Likely the dietician that you see has been educated in what the government suggests. I am not a dietician, but I think they can get into trouble if they stray from the recommendations that they learned in school.
However, you may find an educated nutritionist or dietician that thinks in terms of lower carbs. I think you just have to find the one that aligns with your beliefs.