This article goes into a good amount of detail about the challenges of completing Gaudi's design--especially due to its technical complexity and loss of much of the architect's documentation and models during the Civil War. I hadn't previously heard about the role played by a then-young New Zealander who visited the cathedral [sorry--basilica] in 1979 and has subsequently been instrumental in harnessing the power of computers to super-charge the construction process via such techniques as robotic stone carving.
The article notes that COVID-19-related issues will delay completion of the basilica past the 2026 deadline established not too long ago.
https://www.cnn.com/style/article/sagrada-familia-history-robots-test-of-time/index.html