The complexity of an implementation is a different thing than the complexity of a design, and each determines things like how frequently it needs maintenance or how difficult it is to use. As usual, the devil's in the details.
You can make something that has complexity without making it complicated or expensive to maintain. Take cars for example. There are many cars today that have a barrage of complex features, yet don't have costly maintenance bills and aren't difficult to use. That's because they have been engineered purposefully to reduce that complexity, and because the people that make them are masters of their craft, trying to create a premium product. Materials engineers, structural engineers, sound engineers, mechanical engineers, and more, all work toward the best design possible, to implement the most functionality with the minimum number of defects. They can tell you how likely it is for the paint to begin chipping on a new tailgate due to potential contamination in an alloy. And they'll use that knowledge to make it less likely that you'll have to take your car in for repair.
The software world today - especially where customers are an afterthought (such as backend software) - does not make attempts to improve its design or implementation to reduce the need for repairs. Instead they just "manage" it for you, doing constant maintenance on the constantly breaking vehicle they drive for you, while charging you a subscription fee. (the auto industry noticed how profitable this is, and is now doing the same wherever it can)
K8s is a great example of terrible design and half-assed implementation. It was not designed to be easy to install, configure, operate, upgrade, or maintain. It was designed the way a company designs software for its own internal use: start with some "opinions" that are more about inflated intellectual ego than practicality, throw some shit together that "basically works", and keep introducing breaking changes so it can never be operated continuously without requiring constant reworking and changing how it's run.
If a car were produced like this, nobody would buy it. But it's handed out "for free", so we all just accept it and end up driving this janky-ass school bus that constantly needs its components changed while the bus is running. But you can't ask a regular person to change the parts on a bus mid-cross-country-tour, so you have to hire a mechanic to sit there on the bus. It doesn't have to be that way, it just is because the people who made that bus don't give a shit about hiring a mechanic, they have 10,000 mechanics already.