Unlike the vast majority of SMUPs out there, this one doesn't demand perfection. Your ship can take multiple hits and you aren't expected to dodge an endless barrage of bullets.
Time spent on upgrades and replenishing available ships can be reduced by spending stars (in-game currency). Additionally, after 1000 stars have been spent a store opens that allows removing ads, getting more stars and halving upgrade and replenish times for money.
In a typical bullet-hell fashion, the game requires constant focus, precise control and looks impossible at a distance. But if you are good enough, Danmaku Unlimited 2 can be mastered.
Raiden was designed for coin operated arcade cabinets and as such it was designed to get as much coins as possible. It's not unfair, but it can quickly get very difficult.