ad Jay: (…) We should remember: there are some learners who do actually feel BAD about their accent, even though they may speak entirely clearly and understandably. In my opinion this is something which can really hold people back, or in an extreme case perhaps even inhibit them from speaking at all.
Striving for this kind of ultra-perfectionism is generally a bad thing, IMO. (…)
That is basically what I have been saying in all my vids and been writing here on the forum as well. Perfectionism to me is a bad thing if it makes people feel like a failure just because they don’t achieve their goals. If you strive for an excellent accent and try to do all you can to achieve your goal but if at the end of the day you still settle for whatever result you are able to produce because you know you have given all you had, then striving for as high a goal as possible does not seem a bad thing to me.
But, as I said before, I think people put way too much emphasis on speaking without an accent instead of concentrating on vocabulary and a command of grammar which ensures you are comprehensible to others.
I’d rather speak with an accent but have a rich vocabulary and good comprehension skills. A native-like accent may be the icing on the cake but without a solid foundation in terms of grammar skills and vocabulary the cake will still taste kind of insipid 
However, with regard to David I have to say that he does not strike me as someone who has tried, by hook or by crook, to speak without an accent. It seems to have been something which simply came as the result of his endeavours. He said quite clearly in his video that he loved German from day one and I guess this motivation was crucial. There may be times when despite all your motivation and passion you may not be as “successful” as others, but that is just the way things are. People are good at different things. We can all learn foreign languages, but the level of proficiency will differ due to a variety of factors.
I don’t think you can actually “learn” how to speak without an accent. I have seen people attend phonetics courses at university for years and they still speak with a strong accent, while others just imitate the accent of native speakers and are doing incredibly well. Accent is the one thing where I believe that talent (for imitation) plays a major role.
Besides, I found phonetics always terribly boring and managed to avoid those classes altogether but one. I miserably failed the class for English phonetics, but fortunately could get the necessary credits from another class I took. Despite my failure to pass the phonetics exam, I manage to make myself understood quite well in English.
Personally, I am not too keen on all those “linguistic analyses” (they might be interesting if you want to get into linguistics as such but as a “simple” language learner I just find them dead boring, even though they may work for some people; we simply have to accept the fact that we are different and therefore pursue different approaches when it comes to learning languages), all I do is listen and imitate. That’s it.
As long as I am happy with the results, I don’t really care what other people think. There will always be some perfectionists out there trying to pick holes in anything you do or say. It is best to ignore such people. While constructive criticism is great, I don’t see any benefit in listening to people who are just out there to find fault with whatever you do or who set goals for you.
You need to know what you want to achieve and if not speaking with a native-like accent is something you are perfectly happy with, I think there is no reason whatsoever to feel intimidated or discouraged by people who have managed to speak without an accent.
If you feel good about yourself and your own efforts, the achievements of others can only be a source of motivation. Why should I envy someone or feel intimated by somebody else’s hard work if I am perfectly happy with what I have? Watching others succeed has never held me back, quite on the contrary.