The article makes a lot of mistakes, because I don't think that the author actually cares about textiles at all.
Cotton is not comparable to wool at all. Full stop. If you wear wool for technical reasons--like, because you want to stay warm--then you need to know that cotton will kill you, as will all cellulose fibers that aren't treated to be hydrophobic. Petroleum-based fibers like polyesters, nylons, etc., do not wet the same way that cotton does, but also don't keep you warm in the same way that wool will. Wool is the gold-standard for cold-weather outdoor apparel.
Tencel--which is a type of rayon--is considerably weaker than cotton when it gets wet. The process for making rayon is usually--but not always--a very polluting open-loop system. There are closed-loop systems, but they weren't in common use as of 2010.
Leather is irreplaceable as a protective material. Synthetic leathers lack the abrasion resistance and/or heat resistance of leather. Compare a pair of high-quality leather boots to the highest quality non-leather boots; leather will last decades longer. So you can't compare on a per unit basis; you need to compare them based on practical lifetime costs. In regards to certain protective apparel--such as motorcycle gear--textile jackets simply do not provide the same level of repeatable protection as leather. If you ride your bike on a track, you will be required to wear leather.