Dameon, I would doubt that if one would visit my layout that you would think that there are many limitations when constructing modular. The neatest aspect of modular, besides its portability, is its flexibility. One can change a couple of module and completely change the eras, scene, or theme. I don't see many limitations.
Another good deal is that working with smaller areas, you see progress much quicker. There are drawbacks as modular is more expensive to construct, the price of the portability. Hardware and construction material for the "tables". Working with smaller areas, modules, allows you to concentrate on detailing, and the finer detailing, of the smaller areas.
I have approximately 1400 ft of track down. The layout is flexible, as the grandson could not relate to my interests of the transition era. He was more familiar with AC4400's, Dash 8's and 9's, SD60 and such. Trains he would see when we visited the NS yard in New Haven, Indiana. The main reason I have so many trains. By clearing the layout of all things steam and replacing those modules, I could pique his interests rather easily. The one module that would remain was the turntable, as the yard we frequented does have one.
The funny thing about the grandson's interests is that his favorite engines are the NKP 765, which we were able to see being rebuilt, the NW 611, and the Big Boys, all steam. But when we would run trains together, since he was 4 years old(he's now 16 and driving a car, how time flies), we ran NS diesels, the ones we saw in the yard. He also liked cabooses, so all of the trains had to have a caboose and not an ETD.
I disagree that the purpose of modular construction is for portability, while that is a bonus. There is actually less "dead" space to fill, and the intimidating idea of engineering and building benchwork for a static display is nil. I've seen layouts where the benchwork should be listed on the Seven Wonders of the World. Massive would be an understatement. My layout actually had its beginnings as a display. The first few modules were intended to be used as a dioramas. Big difference in planning and engineering.
Modular is the way to go in my opinion. Not just for its portability, but for the little "victories" one gets when completing each section. The bonuses of portability and flexibility are just icing on the cake. And building is not much more than constructing dioramas, and connecting them.
Bob