As a veteran player that "quit" the server a couple days after ed3 release I can give some feedback on what could help me and others stay
Make PvM higher skill - NOT HARDER
Many people are asking to make PvM harder and there have been instances where bosses were made harder, it's the right idea but very wrong execution. Let's take kalphite king for example, it used to be very easy to afk solo and to compensate, the minions were made into mini magic cannon machines spamming 200-300s on you if you don't have mage prayer. This was a terrible change imo, made the boss more annoying not harder, with no proper AoE to kill the minions people simply find spots to hide from the minions and camp range gear to compensate with magic defense and hope to get magic phase kills
So instead of this linear nerf how about we do something more interesting, for example:
Increase KK's defence/weakness against the combat triangle based on the phase, forcing players to bring hybrid armor and multiple attack styles or form teams with roles. Currently everyone just uses ranged for magic defense + good damage
Add a green attack like Rs3, obviously we don't have abilities but something simple like wear a shield after the green to cover from the insta kill (Make sure to implement an attack cycle like in rs3 where the green always falls in the 3rd cycle or something and not just random)
Add a bleed ability to melee phase that can be cleared by wearing a shield
Fix mage phase balls to have proper timing (they are too fast and cant be dodged without running around all the time)
Add weakness to keris (add desert amulet 4)
Boost Bosses basic drops
Currently, pretty much every boss (other than telos maybe) people only farm them for the rare drops, the side loot is always awful and once the main drop is nerfed nobody does the boss anymore. This would be a deviation from Rs3 style but maybe a big table of random noted skilling supplies that players can reliably sell in ge for a profit (currently only drop that fits this is dragon bones in vindicta). Elite dungeons could really benefit from this, ed2 is 100% dead content after ecb was removed from drop table (I know this is a flaw in rs3 as well), so some actually interesting drops to the minibosses and bosses here would be nice. This applies to ed1 and ed3 as well
Invention
Two main changes I would suggest to invention:
1. Fix the gizmo calculator, either make it 100% like rs3 so that we can use wiki's calculator reliably (also adding inv potions) and be somewhat confident that we can get the perks we want without doing 100 attempts at a combo OR show percentages of success somehow in the creation interface. Also make combos easier to get, bis stuff or any decent combo at all is just pointless to even attempt
2. This can be quite controversial since it deviates highly from rs3 but I think it would make a more interesting and fluid ecosystem to boss drops. I purpose adding custom perks or changing existing perk recipes to make all rare components useful. Gwd1 components are all 100% useless with the exception of armadyl, and as a consequence bandos and sara items are worthless and new players can actually lose money by farming these bosses.
If all rare components had an use, items like bandos, sara items, seismics, noxious items (except scythe) and many others would actually have a value on pair with their rarity and people would buy/sell these much more frequently with the end goal of disassembling them for components, creating more item sinks so the market isn't overflown with them and their price crashes to shit. (take seismic wand/orb going for 30m each in ge and no one buying it...)
Transparency in game changes, drops rates, etc
I know pretty much everyone mentioned this already but please before adding a huge nerf/buff to something discuss it with the community, no hidden nerfs like those done to ed3/ed2 base drop table and a couple months ago to pretty much every boss. Make the examine drop table more reliable, in ed1 and ed3 there are items like rune salvages that show as x% to drop 1-50 yet 90% of the time it drops its only 1? Either make the 1-50 a uniform distribution or share the % changes for the different amounts
Thanks for reaching out and listening to the community, this was very much needed