No, not "of course". Generally speaking, a practice only lasts long enough to become traditional if it works, or at least doesn't make things noticeably worse.
Yes "of course". Just because something "works" or doesn't make things "noticeably worse" doesn't mean that it works
better than a "rationally-planned alternative," or even has any positive effects at all. For example, Chinese traditional medicine prescribes sweet wormwood, which was the basis of an important antimalarial drug...and it also prescribes ginseng, which modern study has shown has a remarkable number of negative long-term side effects. But even in the former case "rationalizing" the traditional medicine by identifying the active ingredient and purifying it into a drug made it work
better than if we simply gave sweet wormwood to malaria patients.
(And then there's the mercury-based potions of longevity, but those were always an elite thing, hence arguably not "traditional" in the sense being used)
And adopting new plants isn't an example of the sort of thing the book under review was criticising. Generally, new plants were adopted piecemeal, by a process of trial-and-error -- some farmer decides to give this new "potato" thingie a try, the attempt is a success, other farmers copy him, and gradually potatoes end up spreading throughout the country. The sort of thing criticised in the book would be more akin to a government official coming along and saying "Right, you ignorant peasants, we've scientifically determined that potatoes produce the most calories per acre of any crop, so from now on you're only allowed to farm potatoes, and nothing else."
And the point
I was making was that traditional practices are not perfect, which is a trap that people (rightly) criticizing the latter often fall into. The fact that they
do change over time shows that they are not in any sense "optimal" and can be improved.
Also, while New World plants did spread throughout Eurasia and Africa, it was often over considerable
resistance from local peasants and farmers--you
did need the equivalent of that official coming by and saying, "Right, potatoes aren't poisonous and tomatoes aren't either, you're going to grow them too" to get people to try them out and realize that, actually, they worked pretty well. It was just that this "official" was more often a large landowner, a feudal grandee basically, and they didn't try to do it to an entire country at once.