There is no such car brand that doesn't have rot issues, Pretty much after 3 years they are rusting away. Cars are built for the lease market
Mazda has a particular issue if you follow the brand, with premature failure of subframe parts for instance. There are NTHSA investigations ongoing. With 30 years of MX5 experience, I am more than au fait with the weaknesses of the marque in comparison to the competition. The NA MX5s rot around the rear sill due to the electroprimed steel (Mazda patented process) being inadequate due to a designed in moisture trap. NB MX5s have the same issue, but now an additional one (and one that is shared by certain Citroens), where they attempted to engineer in improved front crash performance by using telescoping front chassis legs, which now created a new rust point, leading to serious structural failure risk in the front subframe attachment. The NC MX5 shows general rusting all over, due to apparently poorer quality steel. The current ND model is shipped with zero secodanry anti-corrosion coatings. In comparison, for instance, the MGF had far fewer structural corrosion issues. Most Z3s are still virtually rust free, even on the underside. I don't recall any particular corrosion issues with the aluminium tub of the Elise or its Vauxhall/Opel clone.
Different markets have different dynamics; the Japaneser market is mostly private purchasers. The UK market has unusual element of fleet users and PCPs (95% of new car market). PCPs work by ensuring there is a high resale value at the end of the period, so not exactly built to be disposable cars.
In comparison, about 20% of new cars in the US are leased. MX5s sold in Japan and the US (steering wheel location aside) are the same as those sold in the UK.
The global export trade of used cars is huge; 14 million cars according to the UN, and this trade is sustained by a steady supply of reliable 5-10 year old cars from essentially the global North to the global South.
Cars were much more disposable in the past; the average age of the fleet has not been declining, its been increasing, ie cars are kept in service for much longer than they use to. Old gippers/Boomers/Gammons usually throw out lines that cars are not as well built as their Oxford/Cortina/Victor/Marina/Avenger etc, which is of course sheer nonsense. Cars have never been better than now.