They've made melding easier and easier over time.
  • It used to be you'd lose the gear if you failed to meld.
  • It used to be that materia only came from spiritbonding in which you'd lose the gear in exchange for materia
  • Then they added a multitude of ways to earn materia, even some where you pick exactly which materia you want (scrips, for example)
  • Then they removed the loss of gear from spiritbonding. You can have your cake and eat it too.
  • Then they removed the time investment necessary to meld when you have dozens or hundreds of unsuccessful melds
The RNG is fine the way it is. That's the whole point. Even with the RNG they do have, they made it more palatable by making the cost (time, gil, whatever) less than it used to be. Since you no longer lose gear when spiritbonding, materia prices have plummeted. Going through 50 Tier IX materia still hurts less than going through 50 Tier III materia in ARR.