I was out walking today through a forest that was originally planted
Was it used for that purpose? The fact that it's still there suggests not.
I carefully used the word "originally" when I originally wrote that. Not because I expected your response, but it suffices.
You seem to be thinking that the trees I was walking amongst were the ones that were planted in the 1300s? No - they had been harvested one at a time, according to their individual shape and size and the lumber needed for a particular ship, from around 200 to 450 years after planting. In each gap left by each harvested tree, others were planted according to the needs of that century while continuing to serve the needs of centuries past. That century's trees were local use as the re-forestation efforts of the 14th century had relieved the military's shortages, and changed ship building techniques reduced the need for particular shapes of lumber. Without the drive of legislation, the new plantings were changed from oak to the more useful (locally) ash and elm. At least, that's what the owner's tax and payment records tell the historians. Those smaller trees were managed by "coppicing" (check your local forester's dialect for their word) with the trees in a continuous state of replenishment from then until the woodland fell out of use in the early 1900s. (There are a few dozen larger uncoppiced trees ; no one knows why they were treated differently. But they change the ecology of the forest considerably.)
Most (not all, "most") coppiced broadleaved forests in the country were grubbed out and replaced with imported conifer species for clear-felling on a 1-2 century cycle during the last century, particularly in the immediate aftermath of the great pit-prop crisis of Word War 1. Which is precisely why this particular piece of woodland was saved from being grubbed out in the early 1970s (for arable, not forestry ; meh), to be used instead as a nature reserve. Then we had the nightmare of Dutch Elm Disease, which I grew up fighting to control in that wood, and which has now been replaced as a bogey-man by Ash Dieback. Fortunately, since we have a range of tree species in the wood, we can lose any one species without losing the woodland as a whole. That's judgement, not luck.
Forest management is a lot more complex than "see it, fell it, move on to the next mountain". Particularly if you don't have a next mountain to move on to.