To what end do they need to do something different to what they owe their grand success, lol? And you can't "just borrow" everything from a wholly different game. Why don't people go ask Tetris and similar games to let you get a high score easier by dropping convenient blocks to remedy your stupid placement mistakes or any puzzle game to have lower puzzle difficulty/end on level 5 instead of level 99..? Because that wouldn't have any entertainment value to the gameplay and player regardless of their ability to play the games as they are well, duh. Shmups are a genre for hardcore fans to play for score, many offer easy difficulties that people who don't play shmups (or hell, any arcade games, hence their death) religiously might try once and go on to say how it was dumb, they finished in 30 minutes and weren't entertained so they aren't more successful than those without. Anyone who doesn't like this or that "because it's hard" will not fall in love with it because the bosses have low health and don't use all their interesting attack patterns so they don't even need to think/use the mechanics to progress and what, feel good, go to the next boss, that's not fun to anyone either.