From a past biology course discussion, raising important points about the evolution of angiosperms:
Hello Student, Thank you! I love that you wrote about plants, my biological specialty. You wrote: “Angiosperm is one of the most common plant reproduction methods on earth.” The term angiosperm defines a division of plant families, but it is not the term for a reproduction method. That being said, I get the point you are trying to make and it is a good one. Let me clarify.
Since angiosperms pollinate via direct intervention from other biological organisms, a great point you raise, their sexual reproduction processes are more specific than the alternative. For example, conifers are wind pollinated. They are members of the gymnosperm division.
As such, angiosperms have a reason to attract participation from pollinators. They do this with flowers. The flowers are essentially agents of natural selection in plant-pollinator relationships. Since natural selection is such a prominent force in the reproductive processes of angiosperms, great speciation has occurred over time. Angiosperms are vastly diverse, exhibiting countless morphologies to exploit a variety of habitats and pollinator anatomies.
Since this rich story of angiosperms is largely centered around the reproductive competition inherent in their biological plan, it makes sense to think of the term angiosperm as a reference to the plant reproduction method, but the term specifies a branch of biological classification.