Aluminium welding is hardly new or novel tech, all those British RN warships that burnt up and sank during the Falklands were aluminium construction, meaning aluminium welding.
Although you are always going to have problems trying to weld really thin plates together, as would be the case with aviation where weight is massively important, which is what I think you are referring to? But that’s not really an issue with welding aluminium as it is with welding thin plates in general. That’s why even in the auto industry, welding isn’t really used on surface panels, those are usually large sheet metal pieces pressed into shape, and then bolted into place.
The main reasons you see so many small panels with so much riveting on aircraft are for enhanced structural integrity while minimising weight (if you made aircraft external panelling like car bodywork, those would literally warp and sheer off when you pulled even a moderate G manoeuvre or hit really bad turbulence); ease of access/repair; and damage control.
Even supercars are nothing like as complex as fighter or airline aircraft; with their miles of internal wiring, many subsystems, hydraulics, electronics and future upgrade considerations. Can you imagine how hard even routine maintenance and repair will be if the outer shell of an aircraft are mainly large welded pieces?
Anyone who has had any bodywork done on their car knows how expensive and time consuming that is. And while I can drive my car without much if any performance penalties with a dint in the bodywork; the same cannot be said for aircraft.
With riveted panels, each panel is independently secured and held in place, so if a panel fails from wear and tear or damage, the surrounding panels have a reasonably good chance of staying in place long enough for you to land. If it was all welded together, any damage is highly likely to rapidly spread uncontrollably, which is extremely likely to lead to catastrophic structural failure since aircraft reply massively on their external surfaces for structural integrity like an exoskeleton.
