ED has quite a few game mechanics that originally had a big effect on gameplay, but were later heavily watered-down (either because of player outcry or new features made them ineffective).
These mechanics now have such a small effect, they could be removed and it would not affect the gameplay of most people. I wish that FDev would make them have a
slightly bigger effect again, as it'd make the game much more interesting, and for almost no development cost:
* Fuel costs. At one time these were a significant worry (particularly for traders trying to make a profit), but some complained about the cost, so now they are trivial except to newbies just starting out in a Sidewinder. You can run out of fuel, but the cost of buying fuel might as well be zero at the moment.
I suggest that the big ships should require much more fuel (so that the costs become significant), while small starter ships would still be able to afford fuel.... although that might require unrealistically large amounts of fuel, so maybe it's not so easy to fix? So what about larger ships requiring a higher "grade" of fuel (which would cost more)?
* Spacestation docking fees. At one time these were a meaningful amount, but now they are effectively zero. (Actually, I'm not even sure they exist anymore, without checking the game. They are THAT low.) Larger ships should be charged a reasonable sum for docking.
And docking at an Ocellus or Orbis spacestation should cost much more than a Coriolis, which should cost much more than an Outpost, which should cost much more than a planetary Surface Port. That way we'd actually have to weigh-up the cost-benefit of visiting an expensive station against the services we need/etc.
* Ship heat stealth mechanic. You used to be able to get your heat down to "0", so your ship iced-up & became invisible to sensors. This was fun/immersive, but then FDev heavily nerfed this in favour of pressing a button (for silent running) that has almost no discernible audio/visual effect. A great shame. ED's newsletter even highlighted a
video demonstrating it... shortly before they effectively removed it.
* Ship wear & tear due to usage/travelling. Originally ships wore out quickly, just from a handful of jumps/etc, but players disliked having to frequently repair each ship component individually. So FDev massively reduced wear & tear, and then later added a quick "Repair All" button on station menus. So now (I assume) everyone just taps this Repair All button as a reflex, every time they dock, making wear & tear meaningless (except for explorers). FDev even spent a lot of effort making exciting malfunctions randomly occur at lower ship health, but now we only see these in PvP battles aimed at making them happen... 'Never' do they occur from just normal ship usage.
There are many solutions to this, but the simplest one is this: Every time you dock & decide to use the station's Repair facilities, you should be charged a sizeable fixed fee (and maybe have to enter the underground Hanger?). That way you would not use "Repair All" every time you docked, so ship health would gradually degrade, until it became worth while for you to use the Repair facilities. I guess the fixed fee should be proportional the size (and complexity) of your ship, keeping things cheap(er) for newbie Sidewinders.
A more complex solution would be that you CAN still use "Repair All" every time you dock, but this gradually becomes less effective as the ship ages (effectively the ships maximum possible health declines). Eventually you would have to get your ship "Serviced" (like you do every year with your car), which would cost a lot, but restore it's maximum health back to 100%. The maximum health would never decrease below some minimum level (to prevent ships becoming unusable without servicing). This minimum level could be higher for (say) Grade A or B modules, which would allow Explorers to still explore with suitably outfitted ships.
What other 'pointless' game mechanics have I forgotten about? I was going to add "Service, Ship & Equipment limited availability at space stations" to my list, but I suppose that FDev roughly got the right balance in this case (you can't find everything at many stations, but they usually offer enough not to hinder gameplay).