Hello MJ and welcome to our community. 
Try and think of the end goal when your motivation starts to drop, hang in there and it will all be worth it but remember, you have to learn the basic stuff so that you can eventually move on the the more advanced.
Hi MJ, welcome to the community. It can be frustrating to not have the skills to play what you want to play, but instead have just enough skills to play what you are not interested in. If you are still in Grade 1, I understand, because I felt the same way. When you get to Grade 2, blues studies are added. When you learn to play A D and E chords, you could continue with the Grade 1 course, but alternate days with trying blues studies in Grade 2 to see if you make progress. If that is easy, you could also skip ahead to Module 18 in Grade 3 to look at the lesson on open tunings. If you don’t have any lessons on Delta Blues with your favorites, you might look on Amazon at Play the Blues Like…: Acoustic Guitar Private Lessons Series Paperback – August 1, 2018 by Pete Madsen. It’s not too expensive and has video lessons of song selections by Charlie Patton, Son House, etc. I don’t know how good the lessons are, but at least they are relevant. You may find though that you need to learn some basics first, but then you will be motivated to learn.
Hello MJ and a very warm welcome to JustinGuitar and the community.
Many people initially begin with a genre in mind and are turned off by the prospect of learning ‘beginner songs’ or ‘pop songs’ or the songs not on their listening playlist. It is a very understandable and common reaction to acquiring and applying the basics in the early stages.
I would wholeheartedly encourage you to grit your teeth and make the effort to learn songs, learn songs, learn songs. In doing so you are gaining the fundamentals of rhythm (the underlying foundation of music), gaining insight into harmonic musical structure and mastering the fine details and skills you will need.
At some point you will need to seek learning elsewhere as Justin does not really offer specialist learning in altered tuning delta blues. Although he does a little on some styles that push in that direction. So keep going and get the basics solid. Plus, you may just find (as many have done) a taste developing for new and surprising music you did not expect to like.
Cheers
Richard