As others say, with modern electronic components, some types of rigid or flexible wiring boards are not options. There are so many reasons, some of which are for EMC reasons, some types of floodplains or ground plane are needed to block radiation emissions. Wires make great antennas. The surface of the component parts can not be used effectively, or hand-to-hand accidentally does not hear anyone telling you otherwise mostly designed for an infrared reflow soldering.
The hole component continues to be available for old integrated circuit, but not new ones. Some J-component components, ball grid array components, and high density plastic quad flat pack packages are either too difficult to try by hand, or it is not possible to sell them by hand. Since modern components allow high component densities, the capability tends to produce the same requirements for the designer.
Not necessarily, but usually smaller “squares” are easier to sell than bigger ones. High density can only be achieved with printed wiring board and also printed circuit board.Incidentally in the company I use to have, is better seen by customers, so if a customer opens one of our machines, they may be surprised how empty it is.
But many air and surface areas are your friends when you have the heat to remove. Computer aided design tools are much better now. Effective auto routers are still too expensive and, nevertheless, are too difficult to use and use effectively. But automation is available to assist interactive design rule checking manual transitions and combing samples) making manual routing easy to do.
However, some people who have access to the tool, have the manufacturing experience, and the design experience to use the routing tool effectively. Interactive board layouts such as playing guitar, or snowboards are very easy to do but have a lot of practice to do well.