I know there's a little science, and a lot of dogma, regarding the fast carbs+protein post-workout, but I just want to say there are some other ideas regarding nutrient timing proximate to training.
What I personally do is have a protein shake with carbs about 30-60 minutes
pre-workout. The idea behind doing this immediately post-workout with a fast carb is that you get the fastest most rapid uptake of amino acids into the blood and into your muscles. Well, it can be 30-60 minutes before most people take their shake post-workout and then another 20-30 minutes more (at least) before you digest this and it starts absorbing. That's a fair amount of time your muscles are without optimal amino acid supply.
If you take your shake pre-workout, you'll have already digested and absorbed the protein and carbs and they'll be...
all up in yo' bloodstream. You'll have your amino acid supply just when the muscles need it. This is the sort of logic people use to justify sipping BCAA cat **** in their peri-workout drink. But have a whey shake before will pretty much do the same thing and be much cheaper. Whey has a tonne of BCAAs remember, and if you're consuming enough protein in your diet, you can rest assured you're getting optimal BCAAs already and there is a maximum effective dose. I can't really deal with having the shake during training as I don't like having lots of liquid sitting in me when lifting heavy.
The rate of glycogen replenishment is not that important unless you're going to be training again very quickly. If you're taking a day of rest between workouts, you're glycogen stores will be plenty full by the time you're ready for your next workout.
As far as the insulin spike, yes insulin is anabolic. But also protein has a profound effect on insulin production, and I don't think most people realise this. Protein can stimulate insulin to almost the same degree as carbs. But either way, insulin at normal physiological concentrations isn't
that big of a deal. Insulin becomes truly 'anabolic' at supraphysiological concentrations seen only really when taking exogenous insulin. That's not to say it isn't doing anything obviously.
Nutrient timing is complex and there really isn't a strong scientific consensus. There are conflicting studies that can support either case. From what I've read though, there does seem to be a little more weight falling on the side a pre-workout protein+carb shake, followed by a big normal meal post workout. Hell, you could even do a pre- and post-workout shake.
But tbh, nutrient timing doesn't even come close in importance as overall diet and training. Diet (macros etc), training and sleep (recover) combined could easily account for 95% of the importance, or more. Followed by 5% importance in nutrient timing and (legal) supplements.