Welp sorry that's not the right picture, I just posted the first one I could find on Google Images that's not a thermostatic mixer.
My shower tap is more like this actually:
Hot on the left and cold on the right. I have to turn them both to zero to turn the water off, I have to set the correct temperature every time.
Oh yeah, that's more like what I was thinking it'd be. We have that, I basically just remember how many turns I need to get to my desired temp for each, and get the hot tap going first so it's got some time to warm up, but also not be afraid to hop in if the water is cooler than you'd like (Not like, straight cold water) and letting it heat up while you're in there or doing adjustments on the fly
On topic, I was taught 5min showers cause I grew up in drought with no town water. Basically it was get in, wet and shampoo hair, while shampoo sits you scrub the rest of your body, usually soap or body wash on a pouf sponge, rinse body and shampoo all at once, drag lil bit of conditioner through hair, wash out, get out.
Now I probably have 10min showers to avoid the rush that a 5min shower entails, but also still be conscious of the water useage