Good writing is based on evidence, not merely opinion.
Interesting evidence does more than just confirm prior understanding — it complicates, teaches something new.
Vivid description makes readers experience evidence for themselves.
Passionate argument makes readers care about the issue being argued.
Stepwise structure helps readers follow your logic.
A topic is not a thesis. But you need both a topic and a thesis.
Almost all writing aims either to inform or to persuade — or both.
So, besides knowing what you want to argue about your topic (your thesis), you need to know what the reader already understands or believes about your topic — what your essay takes as its starting point, its preliminary understanding.
Journalism tends to take as its starting point the understanding of a typical reader.
Academic writing tends to take as its starting point the understanding of experts in the field.