I usually don’t think it’s a big deal to turn off electronic devices and stick them in the seat back pocket on take off and landing. I also don’t think it’s a big deal to put up my tray table or put my seat in the upright position. When it came to electronics, I always thought the reason for turning off our phones or iPods was to prevent them from interfering with the sensitive electronics in the plane. As it turns out, the real reason has nothing to do with electronics.
The reason they ask you to put all that stuff away is because it can become a dangerous projectile in the event of turbulence or some other jarring force. While it’s unlikely that will ever happen, the probability that you hit turbulence goes way up as you descend (or ascend), so it’s much safer to have those small heavy projectiles tucked safely away.