Too much effort. The whole point of the shmup genre is to just pick up and play and be extremely entertained and engaged. All the good shmups give you intense rewarding experiences from the minute you put your coin in. Why does Otomedius get a free pass? It takes 60 hours to get good doesn't work for shmups.
Like I said the Gorgeous mode fixes that a bunch by being 1 hit death.
Eh, it's like a whole different game if you change the difficulty on the map screen. It's very intense and rewarding if you bother spending a few rounds with it. Plus, versus mode, play it and you'll realize why the game is so popular.
You want to know why Otomedius gets a "free pass"? It's what people want. It's a very casual shooter so anyone can play it without being annihilated in the first round, which causes them to get frustrated and not play anymore. It has a collection aspect so people have incentive to keep playing, other than the obsessive "1cc crowd". They didn't forget the hardcore players though, with the higher difficulties being quite challenging, and versus mode for close competition with other players. It's a new direction for shooters, something that needs to be done to make them relevant in the public eye again, instead of those who just obsess over scores and avoiding beautiful bullet streams.
Otomedius is the most popular shooter in arcades in a long time. Arcades which have no shooting games have Otomedius cabinets with people playing them. It was voted the best new idea in the Arcadia Awards 2008. The 360 port sold extremely well for the genre. It's a new direction the genre might be taking soon (especially with games like Death Smiles being much more n00b friendly, Cave has already announced a sequel to it).