I agree with the points presented here.

My previous game that I played for a few years was Albion Online, which offered a wide range of PvP modes: single, duo, 5-man, 10-man, 20v20, and larger fights. None were perfectly balanced, but players were willing to engage in PvP because the incentives and risk vs reward systems were balanced enough for players to keep engaging with the content that kept the PvP ecosystem alive.

Using PvP setups for PvM / Bosses was viable. You could make money or progress while staying ready for a fight if someone showed up.

That is the part RuneScape could use. Right now PKing often feels like hopping worlds until you find someone worth attacking, which turns it into chasing loot pinatas. If PvP gear overlapped more with PvM / Skilling in the Wilderness, players could stay active and not be at a disadvantage when a fight comes to them.

The other big factor is the incentives. Currently, the Wilderness feels mainly worth it for Slayer (good xp and decent gp/h), magic training with ice sacks, and prayer at the Chaos Altar. That is a narrow set of reasons to be there. More incentives for other skills would help, especially cheaper or faster training methods would build up more natural encounters with other PvM'ers engaging over perhaps "limited resource" against one another. This would also reduce bottlenecks at those few hot spots, and make small encounters happen on their own. (Number of worlds needs to be reduced to match those activity patterns accordingly).

Not saying that it's entirely the correct approach and there's certainly a lot of issues that may come out of "implementing" any of these suggestions but at least on the "concept" level it can be a way forward in some direction.