Yes and no. For the literal first prototype you get out of the door, yes, having some baseline UI work done for you would be nice. For the sake of the argument, let's assume that the code generated by said tool is at least somewhat reasonably structured so refactoring the code isn't a nightmare either. You wire the UI up to some data and get it out of the door to get some feedback. The problem comes after that initial step — you show the first prototype to some test users or stake holders and figure out what needs to change. Integrating the now changed output of the updated UI with the code you already have will no longer be trivial. So long as the prototype is lean, this will be manageable for some time, but sooner or later it will not. The problem is that for most projects, the initial prototype stage is a very miniscule part of the whole product lifetime. Getting one prototype for cheap can be good, but there are UI prototyping tools that can do this. Using those tools instead of trying to reapply the updated output to your now-existing code base will most likely be less work.

In general I do think that tools in this niche will mature over time, but in my very subjective opinion, they won't be the holy grail of cutting down development time. Most of the time, the hard part of software development is the long haul, not the initial kickoff.