I personally have not experienced this issue on my device.
Kudos for checking forums and researching issues with the phone prior to purchasing one. I did the exact same before I just bought the wife a Galaxy S4 Mini yesterday....
My S5 is "ancient" as I have had it since release day 4/11 and never had those problems. ALMOST never..... until 3 days ago.
My home web provider is AT&T on a phone line no less, via DSL. Originally I used a rather dinky P.O. S. DSL modem and my CISCO WiFi router. My S5 would connect to the CISCO's WiFi in about 2 seconds after unlocking the phone. (note my signature, internet is turned off when phone is sleeping).
Okay, called AT&T tech support and they came out to the house and replaced the POS modem with a new toy called a U-Verse device. That fixed my loss of internet problems immediately for the desktop PC, but it created a brand new problem for WiFi and the S5.
Currently I have no way of getting into the UVerse modem and managing how it takes care of WiFi..... it is preprogrammed to "Automatically link up to any kind of security".... Well, that isn't working so well with my S5.....
To fix the problem, I have resorted to NOT turning off WiFi on the S5, I just leave it ON all the time and that resolved "the issue".
And yep!!! forums are the perfect place to hear about perceived bad designs with any manufacturer's hardware. Those who never had a problem never find a forum and start yelling how good their XYZ device is. You only hear from those who for some reason, real or imagined, have a problem.