The main issue here is that p2w people here can take part also in events for f2p and that the quantity of luck needed to be on an even ground with moderate cashers (for moderate i mean people in the range of 50-200$ per month) is way too high.
Imho in games like this one if you pay you should just be able to save a little time and getting way earlier op ninjas. But the point is that also f2p, by hoarding sources and spending wisely, should be able to get the same things whale get instantly in a reasonable amount of time (1-2 months). The problem is just that one, that if you are full free to play you have close to 0 ways to get in 1 year a super rare ninja that isn't outdated or a good basic starting point (level 7+ battle armor, level 8+ refinements).