Why does it take a year to construct an apartment building?

There are some objectively needed times (i.e. maturing of concrete, mortar, paint, etc.) and some (a lot of) times deriving from the general organization of the builder (and of the building industry as a whole).

People (workers) when available are not easily organized as "on demand", in a construction site there are phases when you may want to have 100 people on site for - say - 1 month, but the month before you only need 30 and the month after you only need 30, what happens is that the 1 month time becomes 3 months+, because you top at a constant 30 people for more months.

In some cases you can use sub-contractors for increasing production, but it is not like they are at home doing nothing waiting for your call, they are actually "booked" (often over-booked) months in advance, so you have to sychronize the site with their schedule, then it takes time to do all the contracts/paperwork according to norms, have them approved, etc..

Then there is weather, whether it is too rainy, too cold, too hot or too windy for this or that part of the work usually you have several days a year of no activity possible, and the way the project schedule is conforming to seasons may make a large difference, particularly for periods shorter than 18-24 months.

It's interesting that the more advanced an economy is (and thus presumably the more access it has to machines and technologies that should speed up construction) the slower it actually constructs buildings and infrastructure.

There are a wide number of factors involved and their relative contribution is difficult to determine. Of course for starters people in advanced economies expect more of their buildings - they are built to higher standards and have more complex features which take more labor to produce. Verification that these higher standards are being met is likewise a more involved process. Advanced economies also have much less tolerance for risk - they sacrifice speed for safety both for the workers building the structures and for the end users. Additionally, workers in advanced economies tend to be less willing to go into manual labor fields and operating more advanced equipment requires more skill, requiring those who do go into the field to specialize, and thus while technology may make workers more productive this is offset by having fewer workers on any given project. Then, advanced economies tend to already be built up - you're either building in an already bustling area where extra measures must be taken to prevent disruption, or you're building in an area that was passed over for previous construction, likely for good reason. And finally, advanced economies tend to have more small stakeholders who have more influence - citizens have the means and motivation to raise objections to proposed projects and it's difficult to grease palms to bypass oversight.

Prefabrication can help - work can be parallelized, maintaining standards is less onerous, and it causes on site construction to be less disrupting. Unfortunately the larger the structure the harder this approach is - you need more capital investment for the production facilities, there are fewer customers you can sell to, and the engineering of structures which can both adequately serve their intended purpose and be transported economically becomes more challenging.

More fundamentally, everyone wants things to be better, faster, and cheaper, but you can at most pick two, and it is very difficult to get people to agree to making things worse or more expensive.

My wife constructed buildings in Asia, lol.

The fast ones you see on TikTok were like IBS (Industrialized Building System). The building was prefabricated, the groundwork was done, and the video starts recording as they transport and connect the parts.

Generally it would take about 2 years.

Piling and building the foundation is the bulk of the schedule. This is much harder in dense urban areas where it has to be done carefully.

Then you have all the other pieces - design, manpower, parts, machinery, bureaucracy, tests, redoing failed tests. Then your services like machinery, electronics, plumbing, facades, cleaning up, QA and defect fixing.

High safety projects often go faster because it's accidents that really mess up the schedule. A single death can end up causing months of delays or a hefty "fine".

If you already have a generic design or simple, non clever brutalist design, it goes much, much faster and cheaper.

You mean once the paper work is all done? You need to do excavation, pouring concrete, waiting for concrete to settle down, repeat for each floor. You need materials, workforce, etc. In my country (EU based) there is a large shortage of construction workers and there are no big companies that can take on such projects with all of their own workforce. A lot of work is outsourced or contracted. And if you have one part of the work depending on another then you just need to wait. Like for iron grids to come across the ocean.

As mentioned in another comment, red tape, regulations and general bureaucracy take a long time in addition to the construction process.

For the latter part, 3D printing might become an interesting option, see e.g. this example: https://www.gira.com/uk/en/inspirations/references/3d-house-...

Because it's a linear process, you can't do many things at the same time as you can with a car, for example.