When we talk about someone doing well on hive, we are saying that they are growing, earning, making connections with people, enjoying their time, and making a positive impact on the blockchain. If this isn't happening, they are not doing well on the blockchain.
Now, to the question, does one need to be a good writer before one can prosper here? Just as you said, the answer is No, it requires more than that. In simple words, it is to follow instructions.
What are the instructions? In my opinion, it is to make yourself known to be an author who posts quality content. Engage as much as possible with others on the blockchain, make connections, have fun as much as you can, participate in contests and be consistent even when it feels like there are no results. You never know when all the hard work will pay off. It is a matter of being consistent.
I am sure there would be more amongst others and the ones I have mentioned, and I would like to know them too.