I tried the GI and GL way of eating several years ago.
Disastrous.
Just seemed to encourage me to eat more carbs.
Also, without testing endlessly for 4 or 5 hours after meals to track each 'high fibre' food combo, I thought I was doing better than I actually was, and my next next Hba1c was an unpleasant shock. The carbs still release glucose, it just takes a bit longer.
I find it far simpler to just avoid carbs, and when/if I do eat them keep the portions as small as possible, and eat them after a meal.
Much simpler than doing all those calculations.
Food intolerances also seem to mess the calculations up - in my case, gluten.