I look at the drivetrain as the biggest barometer. When Toyota does iterative design, such as from 20r to 22re to 2rz, they typically make small improvements based on the flaws of prior generations-- so a 250k mile engine may become a 300k mile engine. When manufacturers just start from scratch each generation and skimp on R&D, that is way riskier.
When you look at how many HF3.6 engine vehicles GM sold over the past 15 years vs how many you see on the road now, reliability (or lack of) becomes obvious. There will obviously be outliers, but the fat part of the curve (in terms of miles at failure) is what is relevant. Even when constraining for things like profile of buyer (e.g. subprime buyers will probably skimp on preventative maintenance), it becomes obvious which companies want to make quality cars and those that are mostly subprime finance companies that happen to sell cars (Stellantis, Nissan to a degree).
When you look at how many HF3.6 engine vehicles GM sold over the past 15 years vs how many you see on the road now, reliability (or lack of) becomes obvious. There will obviously be outliers, but the fat part of the curve (in terms of miles at failure) is what is relevant. Even when constraining for things like profile of buyer (e.g. subprime buyers will probably skimp on preventative maintenance), it becomes obvious which companies want to make quality cars and those that are mostly subprime finance companies that happen to sell cars (Stellantis, Nissan to a degree).