Okay. it's not exactly wrong to credit feed, as long as you plan on going back and beating it right later.
Many people once they beat the game that's it. no matter what they did to beat it. If they can't beat it without cheating, they cheat.
With your typical checkpointing unlimited lives game, that's very much a valid way to play the game (well except for the cheating). In fact, that's the right way to play it.
But that's not how to get your moneys worth out of a bullet hell shooter.
And people (including many western reviewers) simply don't understand this.
With free unlimited virtual credits you don't even need a cheat code to cheat, so to speak. Credit feeding a bullet hell shmup for any purpose other than practice is essentially cheating. Sure there's no codes, but it gets you to the end as surely as any invincibility code. And if seeing the end is all you care about. well then you don't get your moneys worth from the game.
The limited credit system is a very good compromise. it lets a player see what's going to happen a bit further into the game, and helps them prepare for beating it for real, but doesn't let them go way past where their current abilities will take them.
On the toher hand, if you single credit clear the game first try.. well... then you probably got ripped off when you bough it for 40$
A few games handled things a slightly different way. The would allow continues, but not on the final level. (Shinobi arcade, salamander arcade) Or they wold force you back to the start of the final level if you continued on it (Silkworm arcade). Either way, the idea is simple. prevent people who aren't skilled enough from reaching the end of the game by pumping quarters.