In my younger days as a programmer, I spent a total of 0 hrs thinking about how people used my products. I coded, and people were simply using it wrong. I then coded a program for tanning salons, something to help them book, scan cards, charge people, run the beds, and then tabulate the finances. Like an all-in-one app for a cash-only business (I learned a LOT about ethics here!) Where I spent 2 months coding (the interface to the beds was painful), I spent 6 months doing the user interface work – back in the day we called it UI. Let me tell you that the ladies working there were trying their best, but 4in press-on-nails do not work with keyboards, or small icons. From that point forward, I had a much different appreciate for ease of use.
A few years ago, the concepts of UI got rebranded to the totality of the User eXperience (UX), which covered more than just the buttons, but how the user feels when they are using it. Amazon is a great example, where the UX has been refined over the years to reduce the number of clicks required to complete a transaction. In quite a few cases, 1 click can place and confirm an order (you shouldn’t use this btw). Apple, under Mr. Jobs, had the UX as a core principle of design. I’ll readily admit that the mid 2010 Apple devices were super intuitive and much better than Android. The stuff just worked.
Games are very similar. Mobile games break with bad UI – the successful ones are predicated on simple interfaces that allow complex execution. Incremental games are successful based on the impression of progress where there is little – AdVenture Capitalist succeeds where many do not.
Controller based games simply need to be responsive. Input lag, slowness, poor button placement, TTK ratios all need to be refined through iteration. The user needs to feel like they have some sense of control of the outcomes. Hades and Dead Cells feel amazing because they are ultra responsive – and also rather simple. Keyboard/mouse games aren’t a whole lot different – LoL works because the interface allows it, and that each click matters.
There are quite a few reports on how Mario Bros on NES was designed with UX in mind. The pace of the obstacles, the music, the gradual increases in difficulty are all reflective of a thoughtful design. The NES is a fascinating exploration of good and bad UX (Battletoads is near impossible because of a crappy UX).
Bad UX on the other hand, dramatically impedes the perception of quality. WoW’s default UI is horrendous, and you’re practically mandated to use mods in order to make any sense of the game – at least with regards to the rails Blizzard wants you to run upon. FF14 is marginally better, due to simplified systems, but you’re still looking at 3-4 hotbars of buttons. Civilization as a series has refined this a lot over time, and looking at any other thematically similar game really makes you question why developers think they can do better (I do think Civ 5 is better than Civ 6 due to this).
Complex simulation games live and die on the ability to relay complex concepts in digestible and layered interfaces. Frostpunk is a set of disasters that need to be addressed before they cascade to total failure. When things are about to fail, you are warned. When they do fail, you get a big notice. SimCity doesn’t readily tell you that something needs tweaking, and you’re often stuck digging through a bunch of variables to see why things are not progressing. Factory games aren’t much different! The supply chains can fail at multiple points and it’s not often clear at a glance as to why. The ability to bring up a production report (Factorio and DSP have this) can give an indication because your consumption is equal to production (or above).
In summary, the general thought on UX is that its reflective of polish. Most QA testing focuses on bug catching, but there’s the risk of the people used to the interface becoming accustomed to it. It’s also quite hard to accurate measure, as it’s often a subjective view. The sort of good news is that most gamers have an appreciation for it, and that more and more ‘reviewers’ are taking it into account, A great UX simply enhances the total experience, and it really sticks out when it’s not present.