Im sorry rory but I will have to heavily disagree here, leveling is the most important thing in nin online, without leveling you will be stuck as a level 1 for ever. If the leveling is not fun for the new players that join they will all leave, id rather (and i think a lot of poeple will agree with me on this) have leveling be made more varied and more fun than to have new things added and fixed. From personal experience I started this game with a group of 7 friends, currently only 2 of play on a regular basis and everyone else has quit before even reaching level 20 (granted the group started in 2021). Trying to convince these people to give nin another go has proven to be very difficult due to their bad experience on the game. On the other hand, it would be a lot easier to convince someone to come back, who stopped playing after level 60 due to lack of content, as their experience was overall enjoyable.
With steam release it is the biggest shot nin online has of gaining a huge increase in players, I understand manpower is limited and I'm not bashing any work done so far (infact I love how the game has progressed) however adding more of a story line, clan missions and more and routes will most definitely have a positive impact on new and older players. All the suggestions and forum posts that Cosbo linked are amazing and are worth taking into consideration. This forum post by Insidious gives some suggestions for new maps and routes:
Some suggestions of my own include, adding a route from the left side of CF that leads towards the leaf warzone, this would allow rogue ninja to have access to Tanzaku without having to cross much of the leaf village territory. In addition to this, adding a route from the right side of CF leading towards asoki port would also allow for a quicker and alternative way for leaf ninja to access the port and also for mist ninja to reach leaf quicker. In general adding a couple maps around the ninja world to link them together would prove beneficial for not only the leveling experience, as you wont have to run through the same route and into the same people, but also for those danger zone fights where someone is camping a map and you cant cross. With the introduction of these new maps could also be the introduction of new mobs and missions which will add variety to the game. Finally, something that you have done in the past is reducing requirements for missions such as waging war and cold blooded killer, reducing requirements for other missions such as clear abandoned lair or any mission that requires killing mobs. Also reducing the amount of items required to complete a mission would also be very beneficial for leveling. For example, medical supply missions require a lot of items that are usually quite hard to farm as they are out of village territory and also the mobs which drop them have a low drop rate or are harder to kill.
I think you should really consider this post and what I have added to it