But in a future where we can rapidly make hundreds of not thousands of efficient robots to work on it? Feels like bungie is just too lazy to fix it...

Where did you saw that we can make hundreds or thousands of robots? And again, its not a small tower.

We see tons of robots all over the place. And during the Devils Ruin quest, we see a ton of trashed robots that have yet to be collected and repaired. There ware also bray frames on Europa. It’s probably safe to say we have some method of making them, and the more people working on a building, especially with futuristic tools and titans lifting massive amounts of material and warlocks telekinetically hauling materials and the ability to transmat materials wherever we want, you would think the tower would be done after 4 years.