Nope, you did not misread it. However, not only merits can make you rank up, but also the activity. This forum's policy has gone through a big change regarding adding the merit system which most of people disagree with. But I consider it as a way to make users improve the quality of their posts. Added to that, you seem a bit annoyed with the new system. Do not worry, pal. I am sure you will get your account ranked up soon enough.
Technically the bolded part is wrong. Both merit and activity is needed to rank up. Previously activity was the sole determinant of the rank of the member. Now both of them are needed, only activity raising wont get you a new rank, you need to reach the corresponding merit too.
Consider this like a demarcation between those who actually post quality content and make thoughtful discussions on a thread rather than people who simply agree to every post. The former deserves merit on at least a few of their posts while the later do not. Thus they will lead the ranks and would be properly marked as "elderly" members of the forum.