I will say that when it comes to insulin dosing, the doctors have to give us a starting point as we are all different in how our bodies react to carbs and insulin.
When I started MDI back in January, my doctor gave me a sliding scale, bolus doses determined by prepradial BG. That didn’t work for me because my before meal BGs tend to be near normal but would rise sharply postprandial.
I had to learn my personal unit to carb grams ratio by the half units as well as learn how long Humalog lasted.
For years I have split Lantus into two doses before I started Humalog. This decreased nocturnal hypos and allowed me to delay the morning dose prior to bike riding. I have been injecting Lantus 3 times per day because no matter the bolus before lunch, 2 to 3 hours after BG would rise as the Humalog levels decreased.
This has worked very well. My 14 day average glucose is currently 108mg/dl 99.5 in range with a couple of faux lows ( I finger stick if Dexcom reports a low without symptoms).
I’m just going on and on, when I just wanted to agree with you about doctors unable to accurately prescribe basal/bolus doses.