My mother died of complications indirectly related to her Type 2 diabetes.
I used to get cross with her about how she ate at times.
I look back at how cross I used to get with her about food and it makes me so angry.... with myself.
The day she died, I was diagnosed with Gestational Diabetes.
Two weeks after I was diagnosed, having not been able to attend her funeral as I was not allowed to travel, I had a poncy doctor tell me that I needed to "try harder" to get my sugar levels under control because I was at risk of harming my baby. Thank GOD, the diabetes midwife jumped in to the conversation to remind him that my mother had just died, I'd had just two weeks to get on top of this, and it wasn't exactly an easy time. He still didn't care. Apparently, I just had to try a bit harder.
Many people who are diabetic, particularly older people, do not really understand the way they have to eat.
This is exacerbated HUGELY by well meaning but shit advice and commentary from friends and family (including, prior to me having GD myself, me). MIL is also diabetic. SIL is always banging on and on and on about her diet. But SIL doesn't have a clue and will melt down if, for example, MIL eats steak because SIL believe sred meat is intrinsically unhealthy and can't understand that while it may or may not have an impact on her heart health, it's 100% irrelevant to her diabetes.
Also, what so many well meaning but ignorant friends and relatives don't see, is how much effort the diabetic is already putting in. This is something that my dad would point out to us sometimes - we'd be ranting about her cake but he would tell us to stop. But then, he was, on a day to day basis, living with her and watching her make mostly good choices day in and day out.
Like a PP, I also learnt it was a lot more complex than saying, "no cake". In my case, for example, I discovered that tomato in any form would spike my blood sugar. A single slice of pizza? Bad. Tomato soup? Bad. Tomato salad? Bad. Spaghetti bolognaise even with almost no spaghetti... bad. I had to learn that. And it was hard for me. for my DM and my MIL who have had an entire lifetime of understanding what is and is not okay, it's harder.
Also, let's not forget that insulin resistance etc, causes a lot of other difficulties in terms of understanding your own cravings/hunger/feeling of fullness. This is because of the diabetes, and is yet another challenge. As someone pointed out, that's why the GL-1 drugs were invented in the first place.