While I agree that things need to be improved in terms of getting people in the project in a timely manner (the suggestion of providing assistants seems good), I don’t think that anyone has a good reason for being demotivated because of this.
I first applied to join Debian in late 1998 or some time in 1999. At the time part of the process of joining was to receive a phone call. At the time I was living in a hotel and they refused to call me on such a line. I could have easily camped out in the hallway of a hotel (the cheap London hotels often had a pay-phone in the hall and no phones in the rooms) and pretended that it was my own phone with an unlisted number. Unless they refused to allow people with unlisted numbers to join (which seems unlikely) then I could have joined then. So it seems that at the time I could only join Debian if I was prepared to lie about my ownership of a phone line.
I wasn’t overly bothered by this – there has never been a shortage of free software projects that need contributions of code. By late 2000 the rules had changed and I joined without needing a phone call. In the mean time I had forked the Bonnie storage benchmark program to form my own project Bonnie++ , created Postal – mail server benchmark suite  and worked on many other things as well.
I have sympathy for the people who apply to become Debian Developers and who have to wait a long time, I’ve been in the same situation myself. But there are plenty of things that you can do in the mean time. Some of the things that you can do are upstream development work, filing bug reports, submiting patches that fix bugs, and writing documentation (all forms including blog posts). Also when projects aren’t yet in Debian it often happens that someone creates unofficial packages, the person who does this doesn’t need to be a DD. Producing back-ported packages for new versions of programs that are in a stable release can also be done by people who are not DDs. Unofficial and back-ported packages provide less benefit for the project as a whole but considerable benefit for the people who want to use them.
There is a lot of work that can be done to fulfill clause 4 of the Debian Social Contract  (Our priorities are our users and free software) which doesn’t require being a Debian developer. It seems to me that if you have the right approach to this and maintain the perspective that Debian is one part of the free software community (and not necessarily the biggest or most significant) then a delay in your application to become a DD won’t be particularly demotivating.