I guess I'm reluctant to accept the fact that the game is designed around getting friends who have better luck than you powerful characters and using them as a necessary crutch to clear higher-level content.
It feels like cheating.
It's honestly a pretty good system for a gacha compared to other games. In this, whaling basically only benefits everyone because someone else's fortune becomes your own. In other games, there's usually some competitive element that gets destroyed by it and you often can't use friend units either.
For now at least, I'd try to see it as a makeshift solution. This early in the game's lifecycle no one outside of players that empty their wallets is going to have a good unit in every class. With the class advantage system being the way it is, it can sometimes be almost necessary to use servants of a certain class to clear content, or at the very least it can make your life a lot easier. Just use friends to patch gaps in your lineup for a while until you get a servant of that class that you're comfortable with up to a good level.
In a way, pulling Jeanne as your only 5* was also bad, because she sits outside of the traditional classes and is only good at not dying because of that and her skills.