Hillwen Engineering is not an old skill and was not made in the old style. There's no manuals, no minigame, the rolls are random, etc. It doesn't match up with the way skills like Tailoring were designed and how they function.
Some of the training is so bad that it literally gives you less points that the skill bar will actually display (the skill progress/EXP bar only displays hundredths of a point whereas ~R5+ Engineering gives thousandths for most training).
It's a production skill to make finished products, and the devs don't like players actually being able to do that easily. Just look at how the Brionac specifically loses 24x the normal durability if you use it on Blacksmithing for an example of how much the devs don't want players to rank up production skills specifically.
Well I tried to word it in a way that made it so that wasnt 100% the case for new skills, however considering they are production skills and perhaps because of how mainstream they made those skills for most new craftable items after its release they wanted to make it difficult to rank so as to give people a reward for ranking it besides just the stats (like having access to a relevant crafting skill).
Well my only explanation for it is what I mentioned before, however you can still prepare a bit for those skills (albeit its a bit more difficult considering how it gets no talent bonuses). I do admit though those skills would probably warrant a bit of complaining to rank, but I wouldnt call it difficult by any means, i would call it monotonous and boring or perhaps costly considering the mats required. However lately nexon has been giving easy methods of ranking such skills like training seals that are tradeable so if you bide your time I'm sure u can lessen the strain.
The Dev's want people to feel like they accomplished something when you rank these sort of skills, give you a reward for all your efforts like giving u access to creating items and weapons that many other people cant create. I personally like this system and it gives you a sense of accomplishment for all the effort and time you put into the skill (even though now its less time and more preparedness/money). About the only skills I really dont understand making grindy are ninja and some of gunslinger.