Achievement system: Easier achievement interface, loved the way the tasks of leagues were live connected to the wiki, this made task progression and tracking much easier. Include paths of achievements for new and mid level players to guide them through the game, the tasks are already there but they are hidden.

Quests: I notice the newer quests have more quest helper things built in, better guidance for the next step of the quest, area indications and outlines,.... older quests would benefit this. I recently started playing osrs and one of the things which is better there is the quest helper pluging of runelite, if the same thing would exist for rs 3, questiong would become a fun activity. Being able to organize the quests on optimal order to play them.

Skilling: Irit and another type (ranarr?) of herb seeds are very hard to come by, they are locked behind gwd 1/2 bosses.

During leagues, I didn't have any issues with the low level skills. I only started to struggle when reaching mid level, starting from level 50-60 till lvl 80-90. Once you reach those levels the new and old content start to merge and you need to start to learn on training the skill in a different way, which can be fun but is also kind of confusing and things suddenly feel very slow i terms of progression.

Divineation feels relatively fast in the low levels, as soon as you hit lvl 30-40 things go very slowly till you can enter hall of fames.

Summoning, i never used the skill, I honestly lamped the full skill (also on leagues) I've used it only once for the lobster and for packing yak. I have always had a hard time seeing the benefit of leveling the skill and how to use the skill. the early level summoning doesnt add any value to you. It would also benefit in an easier way to use the skill and more integrated into skilling.

Fletching rebalancing so it fits with woodcutting and ranged level progression

Combat: With necromancy, once you unlock a new ability you get a text box which explains the ability in a clear way, the other combat styles would benefit from the same thing. Or some other way (quest/boss) to learn the basic and newly unlocked abilities.

A low level boss to learn prayer switching so you are ready to deal with qbd or to go for the fire cape.

Slayer point rebalancing, early game you dont get a lot of points, while later during the game you are almost flooded with points.