You can't just say "80% is wasted" when it's just wood that is used for other purposes than timber. Until we can convince Mother Nature to grow trees which are perfectly straight and preferably already square, the process of converting a cylindrical log to a square beam will inherently have some cutoffs.

The linked article in turn links to a research paper at https://www.woodresearch.sk/wr/201202/12.pdf, and while that paper does support that only ~20% of a tree gets sawn into long pieces of (construction) lumber, it absolutely does not support that the remaining 80% is waste. For example, ~37+9= 46% goes to the production of chip and particle boards, a decent amount becomes firewood, the paper industry takes some "waste" wood as input for cellulose production, sawdust has a variety of purposes and even the leaves and stumps can simply be composted.

It's mind-blowing because it is bullshit and a total misrepresentation of the paper it cites. What the paper says is that less than 20% of the volume of the tree (including the branches and the leaves and the stump) becomes dimensional lumber, 40% becomes chipboard, 7% is firewood, 2.3% is sawdust, and the remainder is burned.

Any time you find yourself surprised by a claim, that's your signal to dig into the sources.

Not to say there's nothing wrong with modern construction, but keep in mind that most roman buildings also only lasted a few decades. You only see that ones that didn't disappear.

Also, do we really want to build houses that are meant to last 2000 years? It seems expensive and very impractical when you want to tear it down to build something new.

The vibe this stuff gives off to me is the "environmentally friendly" materials racket wherein some jerks lobby for some public/private rule/requirement change that's favorable to some product on the basis of the environment and that product is only marginally better for the environment (usually because it takes a recycled thing as one of its inputs) while being substantially more expensive/less performant per dollar. But the people pushing for the change don't care because are or are paid by the people who make the new thing that wouldn't have seen serious adoption without the change favorable to it.