There was still the mechanics
Today, development is quite simple: Take ready-made hardware modules, which are a dime a dozen. Then you program some software and the embedded system is ready. If there were not the mechanics.
In many embedded projects, I find that a large part of the effort is hidden in the mechanical requirements and only becomes visible at a late stage. What is underestimated at the beginning quickly leads to unpleasant surprises and massive overruns of costs and deadlines.
The tasks sound simple, but the implementation requires a lot of coordination and is often time-consuming: How are the electronics attached? What forces act on the circuit board? How do buttons have to be designed so that they also feel good in the housing with keycaps? How do you get the light from the LEDs to the surface of the device and create even illumination? How is the touch screen installed flush and without gaps, and what material should the surface be made of? How tight do we need to get against dust or liquids, and then how do we get the heat away from the electronics?
These are all questions that have a strong influence on the development of embedded hardware and also software and must be taken into account right from the start. The topic really heats up when designers are involved or modular device concepts are to be realized.
One example: It is not uncommon for product management to demand that a family of devices be realized with different operating concepts. A small cheap display for the low-end device, a large touch display for the expensive premium line and another device class in between. Electronics and software would like to be kept uniform, simply plugging in one or the other operating unit would be nice. The components are then selected based on price/performance, come from different manufacturers and are mechanically and electrically incompatible with each other. Now you have to make decisions: Do you let the display manufacturers standardize the connections electrically and mechanically, or do you provide your electronics with different connectors? What does this mean in terms of costs and variety? Simple assembly options must be created for all combinations in order to keep production costs within limits. Where the product management thought at the beginning that one could save money with modular device families, the bitter truth may come at the end that one would have been cheaper and faster with individual developments.