There are a few benchmark levels that comes with significant improvement, being 50(summon unlock), 53 (you can farm out a USEFUL summon) and 55(getting your last passive talent tier). There are others but they are less significant.
But yeah, other than those levels, power is the key.
@OP: most players carry either a heal or a tank in their team (in early game, this tend to be hinata and/or sakura), you can get away with using your main to tank and therefore not running tank and maybe not even healer, so you can do damage through your OTHER ninjas. Frankly, outside of fox and maybe sage, DPS doesn't really matter anyway, grindy is an option. Earth and water are a bit awkward in fox in the early game and are frequently hated in sage. Of course, this is more of an early game concept, there are other routes to go once you get more ninjas and level up more, including a very long lasting tanky team and a more cc route. But if you have to ask, you probably aren't ready for those.
even at those levels power still means more, a lvl 55 with 10k power will never beat a lvl 40 with 20k power the raw stat difference is just too large