I too wish there were less filler cards in each set. I sometimes think TPC is afraid that having too many viable cards will lead to an unbalanced game, so they take the easy way out and make just a handful of viable cards so it's easier to manage.
TPC also seems to focus on collectability just as much as competitive play -- the recent Mythical mini set, for example, is largely useless, but they are geared more towards people who collect. It'd be great if they were viable as well, but for me and others like me, just having them in shiny full-art cards is awesome enough.
So I disagree that a competitively useless card is better off not existing, because lots of collectors would still want them. If I were a Swanna fan, I'd be elated to have the new card you mentioned, despite it being useless competitively. A more personal example would be Sawsbuck; I'd really love to add a new one to my collection, and when one eventually is printed, I also wholly expect it to suck competitively. But I still want it a lot.