Absurd hyperbole. I mean, all someone has to do is just look at the front-page to see that this is false.
> it seems like they shadow ban everyone except for bots
Also absurd hyperbole.
You claim to have been banned because an admin or an algorithm incorrectly identified you as vote spamming, but I honestly don't believe it based on the rest of the content in your post.
The short of it, like many similar platforms from the past, is that Reddit is highly customizable if the user chooses that route (not to mention Reddit Enhancement Suite).
The fact is "raw" Reddit is nothing to write home about and the previous front page worked around that with default subs.
I have no idea how it makes sense from a user conversion perspective, since new visitors essentially see the crappiest sides of Reddit before they even make an account to then go and learn how to filter it. I know personally if the first time I visited Reddit I saw what I usually see on the front page these days I probably would stay accountless
As for shadowbanning, reddit is taking steps to get rid of that altogether [0], or at least they recognize that it's a bad system for actual users.
[0]: https://www.reddit.com/r/announcements/comments/3sbrro/accou...
Undermoderated websites gradually radicalize as the heat and rage drives away moderates. 4chan is the extreme example of this, but Reddit's culture slowly lumbers in the same direction.