onarliog: What good is a shmup if it doesn't overload your senses? :)
For me, these hardcore bullet hell titles are simply pattern recognition games and not really shoot'em ups in the original sense. And with that I mean the general blueprint established by 1980s arcade grandfathers of the genre.
It's just a personal taste of course. I like a challenge, but I'm fond of a design where you still feel you are there in the environment that theme-wise gels with the sprites of your ship and those of the enemies, and it's not merely a wallpaper of death-delivering projectiles.
All you do is look at your hitbox in relation to the onslaught of stuff thrown at you. Overwhelming in that way is no fun for me. Ikaruga, Zero Gunner 2, Under Defeat: just off the top of my head, I loved them on the Dreamcast. But those harder-core games that require you to navigate death-curtain overload all throughout are just not my cup of tea ;)