This isn't a game that's meant to be "beat" in a few months.
It's a game that allows you to make choices on what you want to do and in so doing can progress quickly or slowly in various aspects of the game.
Sure, some people have most everyone 7* but they've been playing for 2-3 years. No one who has everyone has been playing for a short amount of time unless they spent a lot of crystals.
To put it another way, it's not that older players are just given everything, they have everything BECAUSE they've been playing for a long time.
In other words, you're putting the cart before the horse. The longer you play, the more characters you have at your disposal. That's literally the point of playing: obtaining and gearing characters, everything else is just a means to that end.
If they just started giving new players all the characters for free, what would be the incentive for them to play? What would be the gameplay?
I hope I have pointed out how your viewpoint on this is decidedly illogical.