40 year mature conifers also have completely different properties and is subpar for the things oak is great for. A conifer won't work as a mast for example. Fast grown confiers will rot like crazy.

They work well enough for situations where they are protected from the elements, which is why they are used in construction. But an old house made from slow growth, espicially a lot of hardwoods, won't instantly rot when water gets in.

Check out “daisugi,” a Japanese pollarding technique that produces usable timber even faster (basically having one rootstock grow multiple main trunks). IIRC in the 1700’s they were harvesting pine every 25 years

However, it ain’t no replacement for oak. Does smell a lot better, though