: If you don't like a rule, change it. If you don't like
ALL of the rules, find or make new ones!
Most everyone who plays a role-playing game tweaks and tinkers
with the rules to get them just the way they like them.
It's not only common, it's expected - you'll find
that many RPG books mention and even encourage
changing the rules to suit your playing style. If you find
the entire rule system to your dislike, consider scrapping
the rules and using a different system. There are a few
suggestions in the Adventurer's Atlas,
and some of them are even available for free.
: If you want to add something, add it. If you want to take
something away, take it away.
This is the same rule as number one, except it applies
to the game setting instead of the rules. If you feel that
a game is lacking something, and you CAN put your finger
on it, then put it into your game. If there is some element
of a game that you really don't care for, you are perfectly
free to take it out. Not enough ninjas? Too many dragons?
No way to get off of the planet and explore some others?
Do whatever you need to that will make the game more fun
for you and your players.
: If it's not fun, you're not doing it right.
That's not a criticism, it's a bit of advice. Observe
your players and communicate with them. If they're not having
fun playing in the game, if they feel the rules are confusing
or too restrictive, work with them to make the game fun
for them. After all, a game that's no fun isn't worth playing.