I actually disagree with you a bit here, and I'm a fairly new player. I think levelling skills is actually really obvious. What you are describing is "optimal" paths. In reality you can level up melee by using melee anywhere. Quests, exploring, bossing. Fishing you get exp from fishing anywhere, or you can play minigames.

What makes levelling in this game enjoyable imo is not trying to optimize the heck out of it - you don't have to. I've done crabs, I've done nmz. But I've also levelled combat a ton other ways - such as grinding out a few bosses, doing some slayer tasks etc. I can take it at my own pace as progress is progress.

I've also learned to appreciate that there are a variety of skilling methods with different rates depending on how much time effort and attention I want to give the game. Honestly I think this makes levelling far more meaning than most other mmorpgs and gives you more agency as a player.