Not at all. They are generally set out very clearly to make it easy to understand how to play, what makes a win, and what your winnings will be, the paylines, the multipliers, and the winning combinations. Even if they seem too much at first, the games are straightforward and easy to play. You don’t need to know the rules to play.
Knowing the rules just helps you to see what’s happening and to shift your playing patterns to increase your winnings and your chances of winning. You can spend time familiarising yourself before you start playing, or you can check them out one by one as you go. You can also play the demo version first to help familiarise yourself with the workings of a game so that you can make the most out of those welcome bonuses.