I generally know which foods are high GI and low GI, though. I just think it's very, very tricky to get right unless you are willing to sit down and track everything you eat and test multiple times after each meal and keep spreadsheets tabulating the results for all the foods that have GI numbers (which I don't think all foods do). And then of course there's the effects of fat which slow digestion and will compound results, and the effects of protein which cause a slower rise, so you'd have to figure out how to filter out the effects of those things. And that's not even counting the fact that sometimes I:C ratio changes completely from other factors which might make some results complete outliers that would also need filtering.
For me, just keeping on top of adjustments to my I:C ratio, ISF, and basal rate are enough. Maybe when my A1c is closer to where I want it (which has been a years-long journey) I'll get bored and feel like I need something more challenging to work on. For now, I don't see much advantage to checking GI values as long as I know in general what is high, medium, or low GI.
As I said, this may be a completely different story for Type 2s not taking insulin. For them, maybe GI is more important than carbohydrates. But I'd think if someone had to choose between eating LC or low GI, LC would be more effective in general. Eating 25 grams of something is going to probably be better for your blood sugar than eating 50 grams of something that is low GI versus 50 grams of something that is high GI.
Note that I'm not in any way saying a GI symbol is bad! Just that the statement that GI is more important than carbohydrate counting is not true for most people, in my opinion.