I guess the popular view is that bosses are supposed to be a break from normal gameplay and is supposed to be very dodge-centric, but tbh the more i play the more i find stage scoring to be adequately engaging. I find it interesting that while CAVE is most popular dev around here, their boss scoring is rather understated, usually just some form of canceling a large bullet pattern at the right time. Guwange is pretty cool if inconsistent, and it kinda falls into the bullet based archetype as well.
The fact that bosses tend to be 1v1 opponents who are not supposed to die quickly ties many devs hands when it comes to scoring, so prolonged milking and boss looking silly as it shoots patterns that have been misled to empty air is always a threat. I tend agree that bosses are more exciting if you try to let them live as long as possible, but it is uncommon for games to account for this and instead a lot of repetitive milking is more common. Milking is pretty fun in the two games I mentioned imo, since their mechanics account for this during the stages already. In GW it is pretty intense to try and time the reflect, and Psyvariar the exp gain is actually slowed so you cant chain iframes forever.
I dont like systems where you speedkill bosses that much. It looks a little boring, and all those pretty patterns go to waste