The short answer would be yes, up to a certain point. Having the same décor in every room of your home would make your entire house look like a single entity, rather than having a home that looks like many disjointed rooms connected by a single roof. A unified decor makes your home one cohesive unit, and also makes it look more organized. Most importantly, it adds the illusion of harmony, by having your rooms flow naturally into the next room.
Although, this advice should be taken with caution and should not be followed to a fault. Matching rooms down to every single detail would not look good as it would make everyone who enters your home feel like they are confined in a single space. It would make your home seem like a prison with every room having the same of everything. It can also make every room a cookie-cutter version of the last room they entered regardless of if they have entered an entirely different room.
Instead of having your rooms look the same as the next room, you can achieve this sense of harmonious flow from one room to another by painting the walls with gradual paint. Meaning the shade of the paint in one room is a shade darker or lighter than the next. This would make your rooms flow together and achieve that sense of harmony. Just be sure not to use a shade that is too similar or uses a different shade thus defeating the purpose. This is certainly not an easy task but you can do this harmonious home design with proper planning.
You can also achieve this sense in your home design by matching the style of accents or furniture you used in each room. You should, however, design each room in one central style, rather you should use a little bit of a certain style in every room. You can do this with multiple styles as long as you make sure that you do not use too much of one style to the point of overpowering other styles. You should also avoid styling each of the rooms with the same accent or furniture or design texture.
Flooring would be dependent on the size of your home. If your home is small and there are only several rooms, keeping the flooring consistent throughout would look good rather than having the rooms have each of their floorings.
With all these in mind, you can balance having your rooms with the same décor but preventing it look dull and boring.