contest posts are inferior to ordinary posts written by good bloggers in terms of interest.

Most of these "bloggers" are not bloggers. They are simple upvote hunters. I've been publishing online since the late 90s. Back then. When there were no CMS, blog systems or social networks. At that time it was still exhausting in email newsgroups or self-assembled html pages.

A good blogger has no time for such challenges because he has so many ideas and article topics in his head, the day should have 48 hours.

They don't need a topic assignment like a 6th grade essay. Only someone who is as creative as a gray cement wall needs those things.

a platform like Steemit should have some big contests

A few years ago there was an account that acquired interested parties for good content outside the Steem microcosm. For reviews, product tests or ratings of new platforms, apps or websites.

These were not judged by Steemians in upvote circles, but objectively by outsiders who had nothing to do with Steem. They were also very well rewarded.

New Steemit users also had a chance if the quality of their articles was good enough. It didn't matter how big the wallet was or what level of play aka reputation level you had on Steemit.