The 2.4 GHz band is ludicrously over-saturated with both neighboring Wi-Fi networks and non-Wi-Fi devices (e.g. Bluetooth, microwaves, etc.). Walk into any mid-rise or high-rise apartment building in America and look at the list of SSIDs -- if the list is shorter than 50 SSIDs, the environment is relatively RF clean. Same is true for storefront shops and restaurants and office parks. Pretty much every urban and suburban area in America will have some level of external Wi-Fi interference on the 2.4 GHz band.
In most practical environments, any new Wi-Fi deployment on 2.4 GHz (with any vendor) is likely going to suck. There is only so much you can do with three non-overlapping channels when all 11 channels are already noisy. Usually, the “only so much you can do” involves cranking the power up to out-shout everything else, which only serves to pollute the airwaves further and tends to lead to a lot of needless self-interference as well.
Some have claimed that 2.4 GHz is dead, on life support, undead, or the like. Perhaps the best analogy is one of a post-apocalyptic wasteland, where all the access points are screaming and all the clients are fighting like dogs over scraps of bandwidth. Unfortunately, the abundance of old client devices, current and new network appliances for both the consumer and enterprise markets, along with the expected onslaught of IoT devices about to emerge means this Wi-Fi wasteland isn't getting cleared out anytime soon.
Even more depressingly, 5 GHz is rapidly going to become the same type of wasteland in the not two distant future. Two unlicensed bands enter, one unlicensed band leaves!