Warehouse even with a full server was too large. It even had roof and basement access. It could take a full 10 minutes to complete matches.
I don't disagree it was large. However, there are other maps (Urban Works, King) that are really big, and open, and take a long time to complete especially with jumping soldiers and pyros. Despite this both maps are very popular. A big factor to this is the abundance of supplement packs, and good camping/stronghold areas for red. I don't think the size made the map any more annoying than Urban Works' long matches.
The accessibility of the roofs weren't very viable for classes other than demo, soldier, and pyro. Engie would need to be exposed in order to make it up there (not to mention needing to sentry jump/boost) just to get a teleporter up. Bosses could easily jump up and challenge the very open nest.
The cap worked just fine and was an exciting battle sometimes to beat the boss with it.
Again, Warehouse had little to be undesired. There have never been any huge issues, in my experience, that warranted its removal.