Jagex - They broke their own game, several times.
It had a few things going for it. The decent quests(which honestly wasn't all that great compared to a normal RPG and because of the the piss poor combat), the PVPing location, the numerous things you could level up, even the most useless such as firemaking.
Its main thing it had going for it was the comfy feel, the minimalist style and super slow gameplay that helped it. The drop parties, scams, bosses were fun. The piss-poor art style, graphics, audio played in its advantage by being so charmingly minimalist like a handicapped NES game or today's indie games. But utterly it would have been far better to use AION's graphics, music and art style.
The combat that was full of misses/0s was not fun. The painstakingly slow grinding was not fun unless you socialized or had something else going on like a clan, a business, a party, something.
Remove the combat skills entirely and combine Guild Wars with Runescape, it would be interesting to see how it goes. Yes this removes pures and the level limits in the Wilderness.
Other ideas for it would be to make Runescape completely turn-based combat without any real-time elements at all. Thus improving the comfiness.
I would have made the wilderness beyond the mage arena less PvP and more PvE by making randomly generated areas, thus adding some mystery and even horror which combines very well with the comfy campy feel of RS. I genuinely didn't know what to do as a noob when I entered Draynor Manor and couldn't find that tiny window to escape. Losing all your inventory except 3/4 items also greatly played in RS's advantage, but perhaps adding no-risk worlds would have also caused less rage quitting, accelerated heart beats, adrenaline and broken keyboards.
Firefall - Again they broke their own game, by changing the way gear/stats/level up system like 7 times, but doing nothing to the gameplay but underwhelm it more by removing invading enemies and adding elite enemies and missions that forced you to do nothing but cheese and trick the meta, even worse than Guild Wars 1's elite missions.
Firefall in its alpha/early beta was really good. I would have added more blackhole missions/areas and would have allowed the player to go beyond the purple wall that kills you, but only for a limited time. It was really good and just needed quality improvements rather than a different direction and fresh new ideas.
Puzzle Pirates - Great concept, horrible execution. The puzzles, fuck the puzzles. Incredibly challenging to the point it was more about RAW talent and severe luck rather than statistics and experience. Also there were simply too few puzzles.
This game is literally nothing but puzzles, economy and cosmetics. You can own islands, open your own shops, buy your own ships, buy your own house and decorate, buy clothes that disintegrate after 1 month of wearing them. Luckily it does not have a level up system, instead it's based on your talents for super challenging puzzles that are far far beyond their normal counterpaths. You could compete in tournaments and win a lot IF YOU WERE SUPER TALENTED.
Placing 10-100 players on a ship and each person doing an assigned job was an interesting and comfy idea, the horrible execution was the puzzles. You had to be painfully good at them. The endgame was hugely based on economy and starting your own business(owning a shop, island, ship, starting a crew) That and a few more quirks like the horrible click and point movement, everything costing money that was hard to earn,
The economical part of the game was a huge double edged sword. On one side it fully embraces the economy side of MMOs and grinding till you start your own business to become a self-sustained wealthy titan, the ugly side were the noobs which couldn't even own their own ship because it costed too much. Not just to buy the ship, but to buy the supplies and to spend a long time moving your ship between islands was a massive pain in the ass. And then there were monster hunts and clan wars where you could lose your ships.
Really depthful economical end-game, but I wouldn't promote that, it's a bad practice. Instead I'd promote the 100 men on 1 ship monster hunting idea, but it needs a good gameplay.
And get rid of that retarded children's art style. Runescape's wasn't cute and never pandered to children, while Puzzle Pirates's presentation was blatantly pandered to toddlers, despite the game being as hard as fuck and including gambling card games such as Poker+Hearts+Spades which no toddler would know how to play.
Actually there 2 things which ruined Puzzle Pirates - its increasingly bored userbase and 2) the kraken hunting which took out the normal game out of the equation and assured you an immense amount of cash enough to buy your own ship in half a day of kraken hunting, as opposed to 1 month of pillagign or a lucky streak of Poker/Hearts/Spade/Tetris.