If you're willing to put a little time into it and do some trial-and-error you can get amazing results. I've been spending a lot of time with it since the update that allowed them to be raced online and honestly I almost prefer the random generation now. I've come up with some tracks that I never would have imagined on my own and once you learn how it works you can actually have a decent amount of control over it. Sure, it's not perfect and has some weird quirks, but don't give up on it because incredible tracks can be created and that will extend the life of the game infinitely.
Learn to read the topography/elevation lines on the map and you can get an idea of what the landscape will be. It also tells you the elevation change so you can decide if you want a fairly flat track or one with lots of hills and valleys. I generally use 2 different methods when building courses, either proper race tracks that are 2-3 miles long and offer a mix of turns and passing sections, or I create long and twisty courses that are more of a country-cruise type road which might not be great for racing but are very thrilling to drive on. Once you get a few good results you might quickly become hooked on it like I am. 👍