I think a larger point is that when we are doing something for the first time and we feel it is original or at least highly effective, as creative people we feel motivated and perhaps excited. But once we have finished something, we won't feel that initial excitement again if we have to do any kind of redo. That is true for me when composing, and it is also true for me when making these instructional videos. Once I have composed something and I know that it works, that composition will never be as exciting for me again. In rare instances I become remotivated if some time goes on and I have new ideas. What is absolutely frustrating and irritating is when something works very well when I play it but I see something that is not efficient or clear when I look at the score. The only reason that I am able to revisit old compositions and renotate them is that the process is very fast and is mostly a matter of reshaping things mentally. Just imagined how old composers felt if they recognized that something they did before could be written better, but they didn't have new ideas about the music, only about the notation. In that case just the thought of doing the whole thing over again would have been totally unpleasant.

In the case of the C Sharp major prelude by Bach, there are a whole bunch of ways why composers at that time did not write in the key of D flat major. I believe I once did a search for Domenico Scarlatti and could not find one instance where he used this key for one of his sonatas, and this is a man who is famous for doing unbelievably original things. Using the tuning systems of the time, some keys sounded remarkably weird, and this is why Bach's tuning system is called "well-tempered" and not equal temperament. Whatever he used was closer to the way instruments are tuned today, but there were still noticeable differences from key to key. There have been other people who have researched this extensively, but you might get close by hearing a harpsichord player do this prelude. The difference in tuning is rather subtle to the ears of most people.