Isn’t the point of most harem anime that the MC eventually has to choose the “right” girl?
Yeah - kinda. This whole trope would be tied in with the traditional love triangle, in which the different romance partners represent opposing values: "Do I marry the rich and handsome count, just like my family wants, even though I don't love him - Or do I run away with the dangerous outlaw, who I have passionate feelings for, but who can only offer me a life of uncertainty and instability." - And then the story will be about the character exploring these options, discovering their up- and downsides, and finally reaching a decision.
Now this classic setup works well enough for a single volume of a novel, but when you have a long running series this would get stale very fast. There is only so much you can explore between two options. So a lot of harem stories try to compensate by just throwing in more and more love-interests - What about option 3? What about option 4? In the end the protagonist is of course still expected to choose one of them - and I don't think I have seen one of these series where his choice isn't one of the initial two (unless it is a true harem ending, which does indeed happen sometimes).
Can't say I am a big fan of harem series either for this reason. A lot of them are just watered-down love-triangles.