In the limit, though, are these things real roadblocks to app builders replacing SaaS? Paying for reliability/support seems like the only real remaining advantage of SaaS if codegen models get 3-5x better, and even then the bar is the reliability of SaaS apps right now (which in a lot of cases is not that high).

Could imagine a single universal app builder just charging a platform fee for support, or some business model along those lines. (Again, in the limit, I'm not sure that support would be too necessary)