Walkthroughs for custom maps.

... And I think it's very difficult to complete such a map on your own. Are there any people here who only complete difficult maps on their own?

:) Mostly, that's who's here!
Besides, if you look at the reviews here in the thread, you'll often find that they are made for new maps, previously unseen in the Community, often Chinese ones.
Hints for difficult maps are not often needed; the Heroes players have too much experience; it's not easy to come up with something new. I don't know, maybe such difficult maps as Metataxer Revenge or Xiedu do require hints. But most maps do not. And the Lord Rings map is far from the easiest. I completed the mentioned Way Home without hints.
A detailed analysis of the editor, the Prospector program, and planning the Walkthrough greatly facilitate completing any map.
In general, the best advice is to choose a map according to your level of play. Because if you put an unprepared person in front of the aforementioned maps, they will simply stop liking Heroes.