The 3rd gen 3s have been pretty solid... 2 places where they did some unnoticeable corner cutting was the brakes and suspension... the brakes, are "just good enough"... they're pretty good, but don't expect it to do well after a panic stop from 80mph with a trunk of junk... it does the job stopping the car, but it doesn't recover well afterwards... I suppose the "just good enough" design also cuts unsprung weight for handling, but after a panic stop cooking the brakes, I realized it was definitely corner cutting, especially of the fact that the brake calipers, and brake booster are noticeably made in China in a made in Japan car.... never mind the fact that it has a weak brake pedal bracket that's like a noodle, and likes to give inconsistent brake pedal feel whenever it wants to... the 1st gen 3 we got rid of long ago didn't do this despite the fact that it was a basket case of corner cutting everywhere elseI am actually currently looking at something similar as well. Most of the small used cars today are overpriced and you pretty much have to buy something near 200k to be reasonable. This car would have been sold for $4k in my area in today's market and I have seen worse.
Parents have 2 Mazda, I can say that from my maintenance with them they do have some corner cutting outside of the powertrain area, mostly in the brake corrosion and things like interior refinement. As a commuter they are legit reliable, especially if you don't live in places that salt the roads.
If I am going to buy a new low budget non hybrid today I would pick Mazda due to the lack of CVT, and proven non turbo design.
the other unnoticeable corner cutting is the suspension... made in China struts and shocks... they don't seem to last long in the typical pot holed american roads and stiff stock springs
oh and I forgot to mention the 3rd unnoticeable corner cutting... "just good enough" cooling... they could've put in a transmission cooler that's double the size of the stock one like they did in the Mexican CX-5, but they didn't until within the past 5 years in the 4th gen 3s and 2nd gen CX-5... there's no documented reason why, but it seems like there were enough transmission failures due to heat that warranted this production upgrade... I went ahead and did the upgrade along with installing a Mexican-spec CX-5 oil cooler into our 2.5l 3, about a month and a half ago to address yet another corner cutting that bothered me over the years... yup, the European 3 and 323s before that always got engine oil coolers in its biggest available engines until the SkyActiv came along.... they never put them in the 3s except for in the Middle East but did end up doing it in the European 6 which shares the same powertrain and stretched chassis... I wanted safety margins and better reliability, not "just good enough", so I spent years finding used parts to do the upgrade because new is stupid expensive lol