Well, imagine a feature request question is seen by 100 persons; and unfortunately 60 of them don't want that feature; think all 60 respond to the question with casting down-votes. So unfair!
Why is that unfair exactly? In the same reasoning it is also unfair that a popular feature request gets 300 upvotes. All of sudden these user can start to close vote other bad feature request because they posted a good one. Also unfair!
But sure they push the asker to be banned from asking!
Correct! Isn't that what we want? You post one badly researched, non-beneficial, self-centered, ridiculous feature request after the other and we need to spend time on those each and every time without you learning a single bit of the previous failure? Why on earth does the community need to asses your poor proposals over and over again? Why would the system not put an hold on your doomed attempts? Saves your and our time.
Perhaps my example is exaggerated; but that's not impossible
It is exaggerated. If you get quality banned on Meta you should get a badge. It is an astonishing achievement. Let's run some numbers for this meta site.
There are all time 34316 feature request. Of those 21844 had at least one downvote. 12210 had more downvotes then upvotes. 39 questions had more then 55 downvotes. That is a small percentage of feature requests where the downvotes might have impacted the OP, if they had no other positive contributions.
TL;DR The system isn't perfect but it is already reconfigured to cater for the different use of votes on Meta for feature requests. Statistics show the impact of quality bans on posters is low and there where the algorithm kicks in, it is probably warranted. I give you those impacted might disagree with this but for the broader community I don't see an issue that needs fixing.