I absolutely love engineering. It has transformed the game into one with actual shipbuilding, where I can sit on coriolis just tinkering with builds, something you could never do with stock ships, which are option-starved and restricted by limitation to the point of being braindead. The vast array of options that engineering brings gives ships so much personality and versatility, and most importantly the nuances of all the options available to you profoundly rewards game knowledge, as all good character building systems should. The process of it can be arduous, but lends value to what you have through effort spent to obtain it, and rewards game knowledge in its own way. It takes you on a decent tour of all the things that can be done in the game, and eventually, when you are well versed in all the best and fastest ways to gather materials, it comes with a sense of satisfaction for knowing how to do something well. In any case, the ocean of depth the system adds is well worth a little grind. And, to put it bluntly, stock ships are garbage. They feel horrible to fly. They might as well be flying through molasses, and watching their pathetic distributors try to eke out any amount of power is like grinding sand in my teeth. Once you've experienced a fully engineered ship, there's no going back.
The possibilities for builds and the system knowledge to be learned is incredible. You can set up SCBs with specialized boss cells, knowing that the heat cost is spread out over the spin-up time meaning that pushing it to 6 seconds lets many ships hotbank without taking damage. But then you're very vulnerable to feedback rails. Rapid Charge SCBs work much better against players, but now you have to deal with a huge amount of heat in a short time. And how are you going to deal with that heat? Here you have choices, too. Heatsinks are the most effective, but how are you going to match them up against the banks you have? Double banks with double heatsinks, or stagger the banks to double bank on one heatsink, which leaves the second bank vulnerable? Or maybe you'll use thermal vent beams. Are you a hull tank? You'd better know how to balance your resists and module hp with reinforced mods in the right places. Do you have enough HRPs to use military grade armor and bring the resists up with reinforced alone, or will you want reactive armor with thermal resist on the smallest hrp? Is heavy duty or lightweight armor the best for your ship? Of course you'll be rewarded for knowing how easily chaff and heatsinks can be shot off, and going for shielded instead of high capacity. Hybrid hull tank? Here you are rewarded for understanding how much of the fight you're going to have to deal with the enormous drain of broken shield regen and how that can stunt your play, and shipbuilders that know to pick low-draw on their biweaves instead of fast charge for this particular type of build are going to have a nice step up on the competition. Now, how about those lovely Plasma weapons? Finally we can run a full set of them thanks to that wonderful efficient mod... but that's not the end of the story. Maybe you'll go looking for your perfect heat balance between efficient and overcharged/srb. Maybe you'll try to deal with the heat of an all-out long range/focused plasma build so that you can catch your opponent early with your tlb just before they reach their comfortable release point. Maybe you'll cleverly utilize the shot speed modifications available for certain weapons in order to line up the reticles for two otherwise incompatible fixed weapons. Maybe you'll try stacking MJs only to learn a valuable lesson about phasing builds, or have an embarrassing encounter with a seemingly puny Cobra that happens to have reverb mines. I put a lot of time and thought into a plasma speed courier build, with the intention of keeping it at the 851 max speed for drive distributors. Let me tell you, nothing lets you experience just how thoughtfully a ship can be put together quite like a speed build. I tried lightweight plasma but they were too hot, so I went efficient and made up the weight elsewhere. Eventually I had a breakthrough moment where I realized there must be an ideal balance using some lightweight and some efficient plasma, and the weight savings afforded me significantly stronger shields. I remember that day well because it was an immensely satisfying act of puzzling out an ideal min/max solution in a very complex set of options, and it's a joy that would never have been possible without engineering. That ship, and all my others, are prized possessions thanks to the time and effort with which they are invested. With credits being given away by barrel, bucket and handful, engineering is one of the last bastions of accomplishment. A stock ship that you can throw together in 5 minutes at Shin feels like a throwaway in comparison.
I can understand how people would not care for it if they don't do any kind of higher level combat, or if they're just trying to mindlessly enhance what they would be doing at stock instead of really digging into the possibilities of shipbuilding, but the former at least don't really need much of it. Many people won't have a need for much beyond FSD, which requires only one of the starter engineers to be unlocked.