Let's get two things straight, because this appeared multiple times.
1. If an achievement is removed from the main list, it does not matter much whether it is removed altogether or moved into the Legacy section. Because whatever you think about the Legacy section - whether the achievements there don't count or whether they do count, the effect is exactly the same: you are disincentivised from continuing the collection until it at least becomes clear which achievements are going to move into the Legacy section and which are going to stay in the main list.
2. The point that an achievement in the Legacy section is worth more because it is no longer obtainable is a double-edged sword and that sword is *very* sharp, unaffordably so. If you subscribe to the notion that an achievement in the Legacy section is worth more because it is no longer obtainable, you are stuck with a low value collection with tons of unfillable holes. Because you don't have tons of things that can appear in the Legacy section. That's exactly why you don't count items in the Legacy section at all, if you are a collector, because if you counted them, you are just doomed and it doesn't make much sense to collect the scraps that you can collect.
I hope this helps understand the point. No offense, but whenever you hear "it's not removed" and "it got more valuable" wrt a change like this, you can be absolutely sure that whoever you are hearing it from is not a collector / didn't think it through.