It's also probably why a person who plays one mech all the time has slightly better aim than a person who plays different mechs with different quirks and movement mechanics.
Anyway, Overwatch is faster and it's mechanics are different. You just need more playtime with it to train your brain and develop that muscle memory for Overwatch. After a while, you should be a crack shot in that game too if you practice enough.
Now I don't know if getting old does effect any of this. Maybe our reaction time slows or maybe it takes longer to train our brains to develop muscle memory.
Anyway, I wouldn't panic. Play Overwatch for a few weeks and you should notice playing the game feeling like second nature to you (as MWO does now).
Edit: P.S. I hadn't played a shooter other than MWO in quite a while. I just bought Doom a few days ago and my aim was abysmal! I kept over-shooting my aim because it was far quicker than I had been used to. After about a 6 hours with the game though, I can already notice my aim has improved drastically. I'm sure as I beat the campaign and dabble in the Multiplayer, I will play even better. Just need to practice.
Edited by MeiSooHaityu, 25 May 2016 - 06:21 AM.