Color philosophy only applies to humans and other humanoid creatures and planeswalkers of that color, right? A leviathan, for example, isn't thinking about achieving perfection through knowledge. A bat is not necessarily more of a selfish opportunist than a bird.

Not every creature in a color holds that color’s philosophy. Some match other components of the color. Zombies aren’t about power through ruthlessness, but do represent harnessing the power of death.

I think one of the most important things people are overlooking about "once per turn" restrictions is it lets you put power into the card in other place. Morbid Opportunist is one of my favorite cards from the past couple years because having this effect at 3 mana is super powerful and it isn't hard to still get multiple triggers out of it on each players' turn.

An important part of good game design is restrictions. You want to provide challenges that the players have to work through. Figuring out how to get what you want is a big part of what makes games fun.

I hated "triggers once per turn" until I drafted Morbid Opportunist and got to play the "how do I stretch creature deaths across multiple turns" minigame, which was great. It plays a lot better than it reads.

Figuring out how to work around restrictions is a fun part of games. Game designers purposefully put restrictions in your way to make you have to figure out how to get around them.

Is Opportunistic Dragon a bend?

Yes.