There's 2 versions of the CX850M. The older version was a Bronze unit OEM CWT that used nippon-chemicon and taicon caps, a step above the CapXon caps used in the 750w. It was also a 30° rated unit, basically it had issues beyond that temp, which honestly is pathetic when most gaming psus are rated to hold full power output at at least 40° and many at 50°C. Considering the CX line has high worldwide distribution, including a huge indo-asian market where temps often reach well into the 40°'s during the summer and many pc's are not run in air-conditioned environments a 30° unit is a disaster waiting to happen.
The new CXM series is much better and does use all Japanese caps. But it's also Gold rated.
While I can agree with you that you should be able to run a gaming system as long as you have enough watts, and not worry about failure, there's a huge difference in quality and reviews. Many ppl rely on amazon/newegg type reviews as they have no idea Jonnyguru or hardtechx or others exist. So they see the CX get 5 stars and never read beyond it. In reality, most of those stars are for fast shipping, worked out of the box, just started and works great etc. 3 months later when the psu is dead, they don't then go back and edit their posts.
There's also manufacturer claims. There's many psus out there, even by well known pc brands, that simply lie through their teeth about ratings. They'll run high tests under specific conditions, like only upto 25°, and make claims based on their evaluation. So you end up with 500w units, that have the power output of a 400w unit, that fail at 30° or have such a lousy ripple that the DCv line looks more like ACv, both of which seriously affect the lifetime and performance of any other component.
https://youtu.be/f6snWfd1v7M
Corsair doesn't make psus. They put their name on psus and help in developing platforms/designs for psus, and specify certain things in a psu, but they are not the OEM. As far as failure rates go, there are mitigating circumstances. If Seasonic puts out 100k units, with a 1% failure rate, that's only 1000 units that are bunk. If there's 100 of those units in any stores stock, you have a 0.1% chance that you get a bad one. Corsair is huge, they'll not put out 100k units, they have 1M units. At a 1% failure rate, that's 10k bad units, a store having 100 units could possibly see 10 of them as bad. That's a 10% chance vrs the 0.1% chance. Now take price onto consideration. You buy a $30 psu and 6 months later it goes bunk. What ya do? Go buy a new one. Toss the old one. Failure rates are based partially on RMA, has to be. There's no way of any manufacturer knowing just how long a psu lasts if ppl just toss and replace. Who actually bothers to RMA a $30 psu? Not many. So the real failure rate is far in excess of what's reported. You buy a $100 psu and it goes bunk in 6 months, you better believe it sees RMA almost every time, so the expensive units will see a much more accurate failure rate. It's still not 100% accurate, but nothing ever will be as consumers will often toss a working psu due to age, replacing a good 550w because of needing a 850w after a few years, the psu could have lasted days or years more, now it's unknown.