SealinkBF
It has varied over the years. True the end user device needs to be as simple as possible. Nowadays, PCs are so cheap it easier to use them - but they are not processing much data, being a terminal.
The key is that 'every system has complexity' it depends where that complexity lies. A good example is that of the desktop computer. The PC route places a lot of the complexity with the end user, or the person who is maintaining it - thus they are cheaper. Apple decided that they would handle the complexity - so their devices are easier for end users as they are all designed to fit together (intially in hardware now in software) and so they are more expensive. {They are more expensive for other reasons too!} Up until some 30 years ago, the domestic motor car placed the complexity on the end user. A 'manual choke' and other such have all been swept away and the complexity now lies in it's computer and the end user just presses the Start button - irrespective of the outside temperature, etc.
Airlines have a serious problem of complexity and their back office 'main frames' as they were called, have to deal with incredible demands and many systems are linked so that long term planning, short term scheduling, right down to bar snacks can happen. There are all the separate systems for collecting route data for each and every flight and maintenance that feeds back into the schedule and availability of each air frame.
In many companies (I am suggesting many large companies) that central complexity has not kept up to date with new software platforms. The costs and risks of moving to a new platform are HUGE - but so is just patching up the old, as BA has learnt. I am well aware of the enormity of the problem that BA faces, as well as the rest of the IAG group. But, if they create a good system, they can duplicate it for all the companies. It is IAG who have to fix this, not BA alone.
Many companies around the world think of themselves as, say, making and selling a range of canned goods but, actually they are not. They are an IT company that makes and sells a range of canned goods. BA is an IT company that provides aircraft seats.
It is this reversal of technology across the last 30/40 years that has allowed a well known online shopping company to become top of the tree. They are an IT company that started off selling books and then sold almost everything else. Observing BA and their IT failures of the last decades, I conclude that they have not yet learnt this.
I will now sit down to be corrected!