I think you're the one missing the point. What you're saying (or at least the way it's being addressed) is that developers should focus only on contents that caters for production optimisation. You might as well have said that the Science system should never have been implemented at all because there are useless skills that do not help in production optimisation, or that newer generals should not be created because they're only for adventure purposes and not directly related in production optimisation, or that a PVP system should never be implemented because, let's face it, it will be very unlikely that it will be about production optimisation.
Now, don't get me wrong. I agree that production optimisation is the main point of the game. I never said it wasn't. What I'm saying is that developers are thinking out of the box. They're adding features that are not just about production optimisation, otherwise it would be very boring (more than it already can be right now).
Again, I don't disagree with this. They definitely take a long time to make. Assuming you're at max requirements already, it will take 2 years 6months to complete the explorer achievements (though this number is exaggerated because by the time you have max requirements to make tomes and codex, you would have had placed books on some skills that would be counted for the achievements already). Now, "how could that be possibly be an achievement?" is what you might ask. Well, let's see. You can half that time by using bookbinding glue and actually go online to renew book production when the time is up. Not achievement enough? Well, try spamming Bandit's Nest for the chance to get Return to the Bandit's Nest, which in turn gives a chance for book drops [I'm aware of the unconfirmed bug regarding this matter and that's something that developers need to work on].
Effort gets you achievements, at least that's how I see it. From my point of view, the Skills achievement (or any of the achievements, even) can challenge us to work around the "normal method" of gaining them. Feel free to use gems if you want to take the shortcut. For those who work hard in real life and invests money into the game, they earn the right to spend their money, and that in itself is an achievement. I, personally, don't belong to that category and I think most of us don't. However, even though some people spend gems to gain achievements, does that stop us from doing them? I think not. Reason? Well, some players spend gems to build up their islands quickly while others don't.
"Play the game the way to want to" I'm sure that goes around quite a lot. Whether you choose to spend the books in order to get the achievements first or spend them to get your main specialists' "useful" skills first before moving on to the achievement, would be your decision. Whether you rush the game or not, is entirely your decision. Though your decision shouldn't stop others from making their own decisions. Either way, they are still achievements because they require effort [and sacrifice].
I'm just going to ignore the fact that you said something about my username (I know you have been playing since 2012 but I would point you back to the rules).