Starship looks particularly shoddy because it's made from relatively small steel plates welded together. The welding process causes each plate to warp slightly, so the end result looks like a quilt rather than a nice uniformly smooth cylinder. Most rockets don't look like this. Most prototype rockets don't look like this either.
The argument has been that this is good enough to start testing structural features, and probably also good enough to do a little bit of low-stress flying as well. The first argument seems sound. I'm not so sure about the second... there are a lot of welds. At least a few of them are likely to be structurally unsound, and assessing weld quality is difficult.
In any case, for the "real" Starship, they plan to use a technique similar to the one they use on Falcon, where they roll a huge metal plate and then stir-friction weld along the seam. This kind of tooling is difficult and expensive to set up, and the configuration of the machinery and the material depends a lot on the actual design, which hasn't been finalized yet.
Apparently they're using thicker steel then they plan to use on the monolithically constructed version to compensate for weld quality, but I don't know... weld seams are great stress concentrators, and stress concentrations are where fractures are likely to form, and fractures on the skin of a rocket are usually catastrophic failures. All it takes is one defect.