You're right that theories (whether they're "ultimate" or just effective theories) don't have to be simple. In fact, as a physics student I spent many semesters studying QFTs, QED, SM and QCD (our current proven and accepted theories) at University, and believe me, they're not simple or beautiful or whatever. (At least not in the sense that a programmer would call something simple or beautiful.)
Whoever tells you that they are is trying to sell you a pop.sci. book or article.
Beauty is in the eye of the beholder. When I studied quantum physics, I definitely thought it was beautiful, in the same way that I find some algorithms astonishingly elegant.
To your point of the beholder: I find/found the ideas of quantum mechanics beautiful, but I find the Hamiltonian formulation of classical mechanics much more beautiful. I see QM as sort of messy...
...until second quantization (and some Dirac-notation formulations of perturbation theory). Those I enjoyed.
You're right that theories (whether they're "ultimate" or just effective theories) don't have to be simple. In fact, as a physics student I spent many semesters studying QFTs, QED, SM and QCD (our current proven and accepted theories) at University, and believe me, they're not simple or beautiful or whatever. (At least not in the sense that a programmer would call something simple or beautiful.)
Whoever tells you that they are is trying to sell you a pop.sci. book or article.