It's only as repetitive as you make it. Repeat playthroughs I tend to prioritize only what I have to do to get the full ending and not much else. Sure you can collect every Korok, complete every shrine, grind upgrade materials, and complete every quest, but what I love is that you are never forced to do any of those things.
I never played Metal Gear 5, but I'm sure it applies for that game as well like you said!