Another thing that (IMO) is a main cause of the slowdown is the sheer scope of possibilities available on general low-cost hardware these days. In earlier time

Another thing that (IMO) is a main cause of the slowdown is the sheer scope of possibilities available on general low-cost hardware these days. In earlier times you had to work hard to make your code do all the work in a given space. This meant thinking long and hard about which features to implement, let alone how to implement them efficiently (time + space) - a practice which has disappeared somewhat, mainly because it is relatively cheap and easy to just implement it, then optimise if necessary. Premature optimisation while coding can be a big problem, but this need not mean that optimisation should be left until the end - in fact it is a good idea to optimise the design prior to implementation (that is, at the end of the design process) This means implementation can be done relatively quickly as the key features are already decided.