178/178 viewing angles is a very relative specification
Disclaimer: This is a post just to raise awareness and not to solve a technical issue. On the other hand, I would really like to have a chat with a real engineer who knows the technical reasons for this situation, but unfortunately, it is not possible for a mere mortal to get through the huge walls of corporate customer support to some engineer.
What's the problem with the current 178/178 viewing angles specification? It is the fact that in practice, two IPS monitors can have ridiculously different viewing angle behavior, despite the fact that they all promise the "copy-pasted" 178/178 specification.
It is not Dell's problem - every manufacturer depends on their IPS panel supplier and, as the result, any monitor can suffer from the issue. It even does not depend on the price or size of the monitor - I have seen a 32" inch cheap IPS TV that has no viewing angle problems whatsoever and an expensive 24" monitor that has intense brightness fall-off.
The reputable testing website Rtings have also noticed it in their brightness tests, especially the vertical angle tests. Almost every IPS display has some dip at about 50 degrees vertical angle, but some have very deep dips. Dell monitors have been both among the good and the bad ones in this regard.
It's a mystery why some IPS panels have this issue with viewing angles. If LG, Samsung, AOC, Sharp (the most used LCD panel suppliers) have established a technology to produce a cheap IPS that has excellent viewing angles, then why suddenly change things and release an IPS panel that has worse viewing angles? Strange.
You might rightfully ask - does it matter? Well, maybe for most people it does not. Still, it might leave some bad taste in your mouth when your shiny new monitor has worse viewing angles than your 10 years old one.
However, it really matters to visually impaired people. People with vision problems often have to use their monitor at closer-than-normal distances. If the IPS monitor happens to have suboptimal brightness fall-off, a visually impaired person will see the image as if on a TN panel, in which case there was no reason to buy an IPS at all. Here's a simulated image of how two IPS panels can look like when a visually impaired person is reading some text:
The problem is that it is not possible to know it before buying. The display manufacturers will not tell you their real-life viewing angle measurement results (because they, most likely, do not have them - they trust their panel supplier). By the way, manufacturers also do not specify minimum brightness setting, which is important for photosensitive people and for people who prefer to work in dimly lit environments. So, it can be a disappointment when your old monitor had 30 cd/m2 minimal brightness but the new one has 50 cd/m2 and you cannot turn it down as much as you would enjoy (especially to watch a movie in the evening). These days it's all about max contrast ratio and bits and frequencies because that's what marketers have educated us to pay attention to.
Anyway, thank you for reading this. Most likely, it won't change anything at all - corporate CEOs and engineers rarely (never?) read these forums. I hope it will at least help somebody to pay attention to the issue and make a better choice when buying their next monitor.