After getting smacked around by Extinction difficulty I spent some time in the chronicles mode. It has a very gentle progression curve, but after you get to stages higher than 2 levels above your weapon level I think it is, it will get very mean.

But at that point you should have acquired some more powerful weapons, apply them, eat the old ones, upgrade, rinse repeat. Its designed to be replayed and chipped away at.

After getting half way through that I revisited extinction mode and played around with the 'Evil' ship with its customizable weapon loadout, and found it much more manageable, aside from that end boss, still tryna beat that last lvl :P

I think beating the last stage in chronicles will unlock the third and final arcade campaign as well...Definitely plenty to do!

For other games on the more forgiving side, Id suggest checking out

Bullet Hell Monday
Danmaku Unlimited 2
TouHou Makuka Sai ~ Fantastic Danmaku Festival

I've greatly enjoyed these. Along with Cave's offerings ofc (not that they're overly forgiving haha) :)

Playing chronicle mode can help you a lot in learning the enemys patterns and getting a feel for what kind of weapons you like. Its also chalk full of lore if your into that ;) The further up in the stages you got the higher the difficulty will get. i think from stage 12 on youll be playing on "extinction" difficulty, up until stage 30 or so. Its a bit stresfull at the beginning but youll get used to the patterns of enemys and enemy attacks.

As far as Arcade Extinction goes, i had the most trouble with getting past the first boss, since you wont have life to spare at that point, once youre at level 3 or 4, its getting overall more managable, or at least it was for me =)

What can also help you is unlocking a variant that feels good to you, thou that can also be quiet a grind at times.

hope this helps you a bit, and good luck! =)

Just to chime in with my play experience:

I beat the 2 very hard arcade modes first try, played Chronicle Mode until about the level ~18-22 region, then went and played the extinction arcade modes for the first time - I 1ccd them instantly and they felt very easy to beat.

I have yet to 1cc Touhou 8 on normal, though I made it all the way up to the final boss on 1cc pace. I do agree that it is an easy game to 1cc; I have 24 1ccs on easy in that game (too many character and route combinations in that game, lol).

To put it another way: I don't think you need to play another shmup that's easier, based on your skill level; chronicle mode should be the next step I think, as others have said.