Another thing that can help is seizing an opportunity to move up the pack by gaining speed through boosting or airtime. Some times in one swift move you can jump from rear to front. But if you hit another ship from behind you'll lose your speed and energy too, so it's make or break. You need a bit of luck.
It's possible to beat master without sliding or double tap. You can cut into sharp corners with the shoulder button* and overtake other racers. I remember a track like the hand-shaped one being easier for me to finish first on, because of lots of sharp turns.
More recently I started to get the hang of sliding and it's a fun and satisfying technique to master, especially boost-sliding. Took me a while though. I like Red Canyon for practising
Good players are able to use double tap very effectively to go through bends at high speeds and not slide out and incur speed loss. Watching how they tackle tracks on youtube can help you improve too.
* left with Z or right with R. Confusingly, the manual calls this "sliding".
https://www.flickr.com/photos/thecuster58/5498812982/in/album-72157626198701584/