Hmm... engineering is not a purpose in itself, it's a tool used to improve/optimize certain types of gameplay
I think therein lies the problem. I think the opposite is the case - I saw the engineering as a purpose in itself and a vehicle to motivate to keep visiting settlements. You can see it all the time on the forums: People see the suit and weapon engineering, and think: I need to get this done as fast as I can so I can start to play the game! And they grind their souls away, and when they are done, they realize... there is nothing at the other end. There is no higher purpose or next level or end boss that requires you to have the best suit or the best weapon - pretty much everything can be done with store bought gear. Also, there is no "best" anyway, this is highly subjective.
For me, the engineering was giving me a path to travel along. I looked at the available options, made a wishlist of what I would like to achieve, and then just played. While engineering my gear I did have a lot of fun doing settlement missions, partly because choosing different strategies to tackle different missions is fun, but also because I set myself realistic goals and saw constant progression. For instance, I started with a store bought G3 Maverick with backpack and damage, a G3 Intimidator with a scope, and an empty G3 Tormentor - yes, I was sort of lucky. I made a list what mods I would like on those items, and then prioritzed them. Get G4 on the suit, mag size on the shotgun, and stability on the pistol. And then I just played the game.
I saw item after item on my wishlist checked, and the necessary engineer unlocks were more or less a side product of my gameplay. Yes, I did cheese a few unlocks with my own bartender, but I pay alot of money to employ him, so he can do something for me once in a while. Each time I had the materials for something, I did a single upgrade or mod. And then proceeded to the next item. I just played the game, and I did one single 15 minute relog session to gain the necessary Manufacturing Instructions. Yes, I did relog. Sue me.
If you set out with a basic suit or weapon and think "I need G5 and all mods before I can play the game" you are bound to fail and be frustrated. There is nothing at the end of the G5 grind that cannot be done with store bought G3 gear. Grinding eats away your soul. Not saying I have the solution to engineering grind, but if you don't grind and do it my way, you have a lot of fun. I did. Engineering
IS the game.