It's a good way for players to look-back on themselves when they return to a lower-level planet and see other new players go through what you yourself had just experienced a long time ago. Playing a character on a planet was a good way to really help one experience what can be done in the game, usually in the form of taking down monsters, completing story or Heroic Missions that offer good stuff, and having fun in a game.
And when the best gear that you dish out in a Heroic Mission is a Blue (which is worth more than a Green but worth less than an Orange and Purple), you got some major issues. No longer do players gain the satisfactory Heroic Mission Epilogue sequence, ruining the story-driven aspect of the gameplay, you could have at least given players the option to have Heroic Missions Auto-Complete function with an on/off button like you did with Exploration Missions. Where it once took 24 hours to reset, you changed it to an ENTIRE WEEK! Where you once got Modifiable unique armor and gear, we now get these damn Lockboxes containing nothing but Blue Gear! The worst is how they've been upended, you've made them "Auto-Complete" at the end when you do things. However, with the Post-KOTFE version of Heroics, you have retooled them to be absolutely worthless in the long-haul and grand scheme of things. They were perfect for raking up Social Points when Grouped together, and on top of decent rewards they gave out, it also had a nice story-driven aspect to them. The Heroic Missions were a nice little thing to do when on planets: good for when you've reached the end of a Class Chapter and like to take it slow and easy. With Knights of the Fallen Empire, you have removed features from the game that make it even less fun than it already was. Where's the fun in Star Wars The Old Republic?