To be fair, many cathedrals in the past took well over 100 years to build (ie. Notre Dame @ 182 years), and it wasn't an unusual idea at the time construction started that it could take this long.

Of course one would think modern methods would have sped things up considerably, but it wasn't until the advent of technologies this century that things really progressed.

I think many cathedrals like Notre Dame were completed several times. It was 182 years from construction until the last addition was finished. Whereas Sagrada Familia is only now just completing its original design. When I first saw the structure, there was no central tower and no plans to actually build it. But you could see it in the plans in the museum there.

I think you meant the 20th century?

No, this century. The majority of the building was built over the past 25 years. The last 15 years in particular have been a speed run to finish it.

Oh, I misunderstood you to be talking about building large buildings in general, not this basilica in particular.