When I start up, my Start Dia File is in the list of recently used files, and I pick it, then save as another name and move along. Or in the nearly inevitable case where some of those those defaults don't fit what I am doing at the moment, I change the settings.
Don't get me wrong, I have wished for a more conventional way to set defaults on start up. But this is what we get unless we learn to write the code. I seem to recall there was some difficulty providing the change, and it required a lot more work than you might think. More work than those doing it were willing to undertake when a simple workflow change solves the problem.
This is a common occurrence - a new user has a bunch of suggestions (that are often repeats of previous ones from years past) that are not informed by experience with the program, how open source work gets done, and an unwillingness to adapt to what is given. I have had the same reaction myself. If someone points out a functional work around - it may be the path of least resistance to use it. We do not understand the inner workings of SVG, the basis of Dia, and over which the Dia developers do not have any more control over than we do over Dia.
I have been using Dia for more than ten years now. I have looked around and tried other programs, but I have returned to Dia a number of times, because it is very utilitarian. There is actually a community of users that are promptly helpful (as opposed to a number of other open source programs I use), and the program is very adaptable - by the user, without intervention of the development group. In conjunction with Inkscape and GIMP the possibilities are almost unlimited. However, if you have a very specific bit of work like circuit design there are probably a dozen better, freeware or shareware programs that will be better. There is no reason at all for Dia to try to serve that need. Any number of prototype houses will let you download their program.
There are other uses of Dia that are unique, as far as I know, that might not work anymore if Dia was tuned up for circuit design - for instance there are power users of Dia who use it as a code writing tool if I understand the conversations I have seen well. The ability to go into the source and tweak it for your own purposes is greatly valued, along with the ability to make a personal library of shapes. Any suggestions for improving Dia that break these uses of Dia will be rejected.
As far as "individual components" components not working as well as others - this is because the components are made by users willing to donate them to the cause - they were developed for that users purposes - not with another other use in mind. They are free. You can try to make them do what you want, but to expect there to be a seamless functionality among them is an unrealistic expectation. The developers do not make shapes as far as I can tell. They work on the function behind the shapes.
Beyond the fact that some shapes people make not doing what it is you want, the system is seamlessly scale-able. It works well, if you scale the canvas around the diagrams regardless of the shapes used. I think with more experience you will become accustomed to it.
