Does only using one paint brand stunt some ones creativity? I only use tamiya because it's what my shop sells, sure I could order any brand but I like the convenience of having the paint I want/need in 20 minutes. But I see on YouTube people using Vallejo, citadel, Ak and MiG then I wonder does using Tamiya only (which although a superb paint it has extremely limited colors) would narrow ones spontaneity while painting?

Javier,

"...using one paint brand stunt some ones creativity?"

No! In fact, it can enhance your creativity. Some modelers mix their own paints. If you get down to it, you really only need red, yellow, blue, black, and white. Of course, one must spend unreasonable effort to turn those into whatever specific hue you seek. And those 5 don't replicate metallics well!

I use relatively few paints and simply add variances as I go. But I use several different brands because i am lazy and don't want to mix up my own colors.

You can also create differences with washes and glazes.

The real question should be, do YOU feel that your creativity is stunts by using only one brand of model paint?
I would answer your original question thus; if it works for you and your getting the results that you like and are proud of , then no it's doesnt hurt your creativity. If you find that your choice of paint leaves a particular gap in performance or accuracy , then I would definetly advise you to search or a replacement , regardless of manufacture. There are plenty of people on this and other sites that will eagerly give you advise. Never feel that b cause one or more people does something that you don't that your doing something wrong. Build for yourself.