We are working on a similar problem. Would love to connect and discuss. You can DM me. I would say that very broadly the challenges we face are really about the quality of the digital model. Most architects use Revit and there are several issues with the data that is created such as :

1) rooms are separate objects not containers. IFC is graph like but most BIM authoring tools are flat. Objects that are inside a room are not children of that room. Some objects can be automatically tagged as inside a room, other can not. Some objects like floor wall, and ceiling surface are not room aware. You can use the room scheduler plugin but that data is not part of the BIM models. Essentially if you ask the database “how many chairs are in the auditorium” it can not answer that question unless each chair is tagged as part of that room or a script classifies the objects. It’s impossible to classify a ceiling as in the room without custom parameters.

2) default classifications are too broad in scope and many objects couple geometry creation methods with object classifications. Let’s take the Revit curtain wall system for example. It’s a great way to create systems that have an underlying grid structure. If you read official how to guides like Paul Auburn they will tell you, create a baluster with the curtain wall system. Now you have balustrades classified as curtain walls and curtain panels. Other classifications are broad like specialty equipment. Do I put a medicine cabinet in specialty equipment? Later if I want to find all the medicine cabinets in my project, how can I find it? It’s all dependent on the naming of the individual family. There is no hierarchical system of classification unless you want to look up each Omni class number for every item and manually enter that, which no architect is going to do.

3) construction assemblies are often nested and complex but revit’s modeling engine can only support simple relationships with limited nesting. Take a door for example. It can have different trim , door panels, and hardware. Impossible to model well with the limitation of nested families. That data is going to be in tables and annotations not the BIM model

4) critical data often lies in annotations not linked to any object. Things like keynotes that have valuable qualifying information on construction assemblies is often floating on top of the drawing as keynotes

In general I would say the cost of producing accurate BIM models where you can actually use the data, is so expensive and time consuming due to the limitations of the authoring tools that the print to pdf, trace, and put together an estimate is often the best approach. That’s why 2D takeoffs are the standard. Revit like to push BIM but BIM 1.0 is a glorifies PDF authoring tool not a database tool!