I remember when I was making coasters in Newton 2 in a few hours. I think as you get experienced you learn more and more about what's right and wrong with your coasters and their transitions and eventually you take the time to get exactly what you want in newton. Now it takes a few weeks of tweaking here and there to get exactly what I desire, but it's worth it because I'm satisfied with the result.
Of course, this doesn't apply too much to wooden coasters because they can basically do anything and still be feasible/possible.
I would suggest putting more effort into your tracks. They seem really bland and could use a lot of work to be more original and creative. Try making them more twisty and less stretched out. Also, add some terrain and trees. The main things that get you good ratings is trackwork and scenery, and so far the woodies you showed us lack both of those.