That sounds like a reasonable view, although I think many mathematicians suspect the world of abstractions is metaphysical (Platonic) rather than just subjective.

I'd add what Lee Smolin does, which is the game-like, fictive quality of math, since once "evoked," the abstractions have logical implications, which may or may not be useful in the real world.

And it's because of that capacity for exquisite coherence that many mathematicians are platonists. The abstract pieces fit together too well to be a coincidence or a mere work of imagination.