I would say that sports betting is both skill based and luck based. It depends on how much time you put into researching teams, players, coaches etc. You need to know the sport inside out in order for it to be successful. The more research you do before placing bets, the better chance of winning.

You are right, the success in sports betting is not only based on one but on both factors (skill and luck) and without them both, a gambler will have a low win rate compare to someone that has a great skill in analysis for good prediction.