To all these nonplayers that like to go all DAD GOOD DANMAKU BAD, as someone who plays shmups and prefers dad:
Cave being so popular to play is 100% justified. The games are more tailored made for high level play. Sure, Gradius games are fun, but optimizing an infinite game doesn't compare to a finite game. Some dad isn't infinite, but there's less to do. So naturally advanced players will gravitate towards games with a high density of stuff to do and optimize.
Take iconoclast for instance, he likes to focus on a complex game to score, namely DOJ, but he also likes to clear some dad games here and there for a less intense but still fun experience. He prefers DOJ because the situation couldn't be flipped, focusing on simpler games would get old faster, and DOJ has a lot to give to the player. Hence why his top of the list has games like this and a bit later he includes some of his favorite dad. He also plays other arcade genres such as beat 'em ups similar to how he plays dad shmups.
As for me, I prefer less commited survival play for my personal fun. I find dad games a bit better when it comes to this, but danmaku are nowhere near bad.
Reserve this danmakuck rejection to people that only play danmakus, which are typically scrubs who only play easy ones here and there (because they don't want to memorize), or 2hufappers (those games suck for score, not even they like them for score).
And finally, less crying and more playing, of course. Participate in that Star Soldier competition and prove your dad worth.