I think there are several problems with medium's proclaimed aim to 'increase quality'.

One is that the curators themselves apparently have a somewhat haphazard concept of the term. I wouldn't bother editing to improve boosting chances - it's like shining your shoes for a parade ground inspection by a blind general.

Another is that they sure as hell don't know what their users think of as quality (and in most cases, that is not the kind of stuff they would want to promote editorially, because garbage readers like garbage writing, and they make up the vast majority).

But also, by constantly hammering in the wedge between boosted and non-boosted, they actually discourage good writers from writing. Chumps who churn out the crap that fills the Medium sewers will carry on regardless. Proper writers, meanwhile, who care about and craft their output, get fed up of it being treated and rewarded in exactly the same way as 'what I had for breakfast' blog posts, and think 'why bother?', as you point out here.

The net result is that the boost actually brings down the average quality of content on the sight.

Slow hand clap for Medium...

What is needed is an intelligent distribution system that actually rewards 'not boosted, but still good quality, from a previously boosted writer' stories, by delivering them to the right people in sufficient numbers. That simply doesn't happen.