I can see the "old me" in this article. I used to carry so much stuff, including 2x or 3x the amount of water I really need for the whole day.
A rather severe back injury changed that almost 15 years ago. During my recovery, my back was very fragile and I was getting recurring lumbar sprain episodes. My life changed a lot when I removed the bladder from the pack and only used a wager bottler on my bike...which led me to ditch the pack for a minimalist fanny pack (Lab Austere) soon after. Basically, I went from over-prepared to super-minimalistic for medical reasons (which sucks), but I really prefer my new setup.
The only things I carry now in my bum bag: Multitool, bacon strips, car keys...and a little towel (for sweat management). I have a pump on my bike too.
I now only ride with a pack when I'm on big mountains in the Alps or when I ride in cold weather.